← Benches
ladder.coding.lru_cache
CodinggauntletAn owned ladder bench, graded mechanically against a fixed test.
Solved
32/35
runs passed
Models
22
have attempted
Harnesses
5
scaffolds tried
Runs (latest per model × harness — solved sorted first)
| Model | Harness | Result | Turns | tok/s | Latency | Ctx | When |
|---|---|---|---|---|---|---|---|
| gemma-4-26b-a4b-it | bare | PASS | — | — | 8.7s | 64k | 2026-06-23 |
| gemma-4-26b-a4b-it | dev_cycle | PASS | — | — | 8.7s | 64k | 2026-06-23 |
| gemma-4-26b-a4b-it | structured_feedback | PASS | 1 | — | — | 64k | 2026-06-23 |
| gpt-oss-120b | baseline | PASS | 1 | 53.0 | 4.3s | 64k | 2026-06-23 |
| gpt-oss-20b | bare | PASS | 1 | — | — | 64k | 2026-06-23 |
| gpt-oss-20b | dev_cycle | PASS | 1 | — | — | 64k | 2026-06-23 |
| gpt-oss-20b | structured_feedback | PASS | 1 | — | — | 64k | 2026-06-23 |
| granite-4.1-8b | baseline | PASS | 1 | 22.8 | 6.0s | 128k | 2026-06-23 |
| llama-3.3-70b | baseline | PASS | 1 | 2.8 | 1.9m | 64k | 2026-06-23 |
| qwen3.5-4b | dev_cycle | PASS | 2 | — | — | 64k | 2026-06-23 |
| qwen3.5-4b | structured_feedback | PASS | 2 | — | — | 64k | 2026-06-23 |
| qwen3.6-35b-a3b | bare | PASS | — | — | 1.8m | 64k | 2026-06-23 |
| qwen3.6-35b-a3b | dev_cycle | PASS | — | — | 1.8m | 64k | 2026-06-23 |
| qwen3.6-35b-a3b | structured_feedback | PASS | 1 | — | — | 64k | 2026-06-23 |
| devstral-small-2-2512 | baseline | PASS | 1 | 8.5 | 45.9s | 128k | 2026-06-23 |
| mistral-small-3.1-24b-instruct-2503 | baseline | PASS | 1 | 8.6 | 16.4s | 128k | 2026-06-23 |
| qwen3.5-122b-a10b-cluster | baseline | PASS | 1 | 17.1 | 4.7m | 64k | 2026-06-29 |
| gpt-oss-20b | baseline | PASS | 1 | 78.9 | 5.9s | 64k | 2026-07-01 |
| qwen3-coder-30b | baseline | PASS | 1 | 36.4 | 4.1s | 64k | 2026-07-01 |
| gemma-4-26b-a4b-it | baseline | PASS | 1 | 28.3 | 14.0s | 64k | 2026-07-01 |
| qwen3.6-35b-a3b-or | baseline | PASS | 1 | 146.4 | 54.4s | 64k | 2026-07-01 |
| gemini-2.5-flash-lite | baseline | PASS | 1 | 36.6 | 6.2s | 64k | 2026-07-01 |
| qwen3.6-35b-bf16 | baseline | PASS | 1 | 34.5 | 1.7m | 64k | 2026-07-02 |
| granite-4.1-30b | baseline | PASS | 1 | 7.4 | 26.3s | 64k | 2026-07-02 |
| qwen3.6-27b | v1.7.1 | PASS | 1 | 8.1 | 1.2m | 64k | 2026-07-02 |
| qwen3-next-80b | baseline | PASS | 1 | 45.5 | 4.4s | 64k | 2026-07-02 |
| qwen3.5-4b | baseline | PASS | 1 | 44.3 | 37.9s | 64k | 2026-07-02 |
| phi-4-reasoning-plus | baseline | PASS | 1 | 14.3 | 2.6m | 64k | 2026-07-02 |
| deepseek-r1-distill-qwen-32b | baseline | PASS | 1 | 6.4 | 3.7m | 64k | 2026-07-03 |
| qwen3.6-35b-a3b | baseline | PASS | 1 | 55.2 | 9.4s | 64k | 2026-07-05 |
| qwen3.6-27b | baseline | PASS | 1 | 7.7 | 1.2m | 64k | 2026-07-05 |
| claude-sonnet-4.6 | baseline | PASS | 1 | 55.7 | 3.5s | 195k | 2026-07-06 |
| qwen3.5-4b | bare | fail | — | — | 24.3s | 64k | 2026-06-23 |
| qwen3.5-2b | baseline | fail | 1 | 96.2 | 6.8s | 64k | 2026-07-02 |
| qwen3.5-0.8b | baseline | fail | 1 | 174.6 | 3.1s | 64k | 2026-07-02 |
Transcripts
gemma-4-26b-a4b-it · bare · PASS
```python
from collections import OrderedDict
class LRUCache:
"""
An implementation of an LRU (Least Recently Used) Cache.
Uses collections.OrderedDict to maintain O(1) time complexity for
both get and put operations by leveraging its doubly linked list
and hash map internal structure.
"""
def __init__(self, capacity: int):
"""
Initialize the LRUCache with a positive integer capacity.
"""
if capacity <= 0:
raise ValueError("Capacity must be a positive integer.")
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key: int) -> int:
"""
Return the value of the key if it exists, otherwise return -1.
Accessing a key moves it to the end (most recent position).
"""
if key not in self.cache:
return -1
# Move the accessed key to the end to mark it as most recently used
self.cache.move_to_end(key)
return self.cache[key]
def put(self, key: int, value: int) -> None:
"""
Insert or update the value for the given key.
If the capacity is exceeded, evict the least recently used entry.
"""
if key in self.cache:
# Update existing key and move to end
self.cache.move_to_end(key)
self.cache[key] = value
if len(self.cache) > self.capacity:
# popitem(last=False) removes the first item (the least recently used)
self.cache.popitem(last=False)
```gemma-4-26b-a4b-it · dev_cycle · PASS
```python
from collections import OrderedDict
class LRUCache:
"""
An implementation of an LRU (Least Recently Used) Cache.
Uses collections.OrderedDict to maintain O(1) time complexity for
both get and put operations by leveraging its doubly linked list
and hash map internal structure.
"""
def __init__(self, capacity: int):
"""
Initialize the LRUCache with a positive integer capacity.
"""
if capacity <= 0:
raise ValueError("Capacity must be a positive integer.")
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key: int) -> int:
"""
Return the value of the key if it exists, otherwise return -1.
Accessing a key moves it to the end (most recent position).
"""
if key not in self.cache:
return -1
# Move the accessed key to the end to mark it as most recently used
self.cache.move_to_end(key)
return self.cache[key]
def put(self, key: int, value: int) -> None:
"""
Insert or update the value for the given key.
If the capacity is exceeded, evict the least recently used entry.
"""
if key in self.cache:
# Update existing key and move to end
self.cache.move_to_end(key)
self.cache[key] = value
if len(self.cache) > self.capacity:
# popitem(last=False) removes the first item (the least recently used)
self.cache.popitem(last=False)
```gpt-oss-120b · baseline · PASS
```python
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity: int):
if capacity <= 0:
raise ValueError("capacity must be positive")
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key: int) -> int:
if key not in self.cache:
return -1
# Move to end to mark as recently used
self.cache.move_to_end(key)
return self.cache[key]
def put(self, key: int, value: int) -> None:
if key in self.cache:
# Update existing entry and move to recent
self.cache.move_to_end(key)
self.cache[key] = value
if len(self.cache) > self.capacity:
# popitem(last=False) pops the least-recently-used item
self.cache.popitem(last=False)
```granite-4.1-8b · baseline · PASS
```python
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key: int) -> int:
if key not in self.cache:
return -1
else:
self.cache.move_to_end(key)
return self.cache[key]
def put(self, key: int, value: int) -> None:
if key in self.cache:
self.cache.move_to_end(key)
self.cache[key] = value
if len(self.cache) > self.capacity:
self.cache.popitem(last=False)
```llama-3.3-70b · baseline · PASS
```python
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key: int) -> int:
if key in self.cache:
value = self.cache.pop(key)
self.cache[key] = value # Move to end to mark as recently used
return value
else:
return -1
def put(self, key: int, value: int) -> None:
if key in self.cache:
self.cache.pop(key)
elif len(self.cache) >= self.capacity:
self.cache.popitem(last=False) # Remove the first (least recently used) item
self.cache[key] = value
# Example usage:
if __name__ == "__main__":
cache = LRUCache(2) # Capacity of 2
cache.put(1, 1)
cache.put(2, 2)
print(cache.get(1)) # Returns 1
cache.put(3, 3) # Evicts key 2
print(cache.get(2)) # Returns -1 (not found)
cache.put(4, 4) # Evicts key 1
print(cache.get(1)) # Returns -1 (not found)
print(cache.get(3)) # Returns 3
print(cache.get(4)) # Returns 4
```qwen3.6-35b-a3b · bare · PASS
```python
class Node:
def __init__(self, key=0, value=0):
self.key = key
self.value = value
self.prev = None
self.next = None
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
self.cache = {}
# Dummy head and tail nodes to simplify list operations
self.head = Node()
self.tail = Node()
self.head.next = self.tail
self.tail.prev = self.head
def _add_to_head(self, node):
"""Add node immediately after the dummy head."""
node.prev = self.head
node.next = self.head.next
self.head.next.prev = node
self.head.next = node
def _remove_node(self, node):
"""Remove a node from the doubly linked list."""
node.prev.next = node.next
node.next.prev = node.prev
def _move_to_head(self, node):
"""Move an existing node to the head (mark as recently used)."""
self._remove_node(node)
self._add_to_head(node)
def _pop_tail(self):
"""Remove and return the node just before the dummy tail (least recently used)."""
node = self.tail.prev
self._remove_node(node)
return node
def get(self, key: int) -> int:
if key not in self.cache:
return -1
node = self.cache[key]
self._move_to_head(node)
return node.value
def put(self, key: int, value: int) -> None:
if key in self.cache:
node = self.cache[key]
node.value = value
self._move_to_head(node)
else:
new_node = Node(key, value)
self.cache[key] = new_node
self._add_to_head(new_node)
if len(self.cache) > self.capacity:
# Evict the least recently used item
lru_node = self._pop_tail()
del self.cache[lru_node.key]
```qwen3.6-35b-a3b · dev_cycle · PASS
```python
class Node:
def __init__(self, key=0, value=0):
self.key = key
self.value = value
self.prev = None
self.next = None
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
self.cache = {}
# Dummy head and tail nodes to simplify list operations
self.head = Node()
self.tail = Node()
self.head.next = self.tail
self.tail.prev = self.head
def _add_to_head(self, node):
"""Add node immediately after the dummy head."""
node.prev = self.head
node.next = self.head.next
self.head.next.prev = node
self.head.next = node
def _remove_node(self, node):
"""Remove a node from the doubly linked list."""
node.prev.next = node.next
node.next.prev = node.prev
def _move_to_head(self, node):
"""Move an existing node to the head (mark as recently used)."""
self._remove_node(node)
self._add_to_head(node)
def _pop_tail(self):
"""Remove and return the node just before the dummy tail (least recently used)."""
node = self.tail.prev
self._remove_node(node)
return node
def get(self, key: int) -> int:
if key not in self.cache:
return -1
node = self.cache[key]
self._move_to_head(node)
return node.value
def put(self, key: int, value: int) -> None:
if key in self.cache:
node = self.cache[key]
node.value = value
self._move_to_head(node)
else:
new_node = Node(key, value)
self.cache[key] = new_node
self._add_to_head(new_node)
if len(self.cache) > self.capacity:
# Evict the least recently used item
lru_node = self._pop_tail()
del self.cache[lru_node.key]
```devstral-small-2-2512 · baseline · PASS
```python
class LRUCache:
class Node:
def __init__(self, key=0, value=0):
self.key = key
self.value = value
self.prev = None
self.next = None
def __init__(self, capacity: int):
if capacity <= 0:
raise ValueError("Capacity must be positive")
self.capacity = capacity
self.cache = {}
self.head = self.Node() # dummy head
self.tail = self.Node() # dummy tail
self.head.next = self.tail
self.tail.prev = self.head
def _remove_node(self, node: Node):
prev_node = node.prev
next_node = node.next
prev_node.next = next_node
next_node.prev = prev_node
def _add_to_head(self, node: Node):
node.prev = self.head
node.next = self.head.next
self.head.next.prev = node
self.head.next = node
def get(self, key: int) -> int:
if key not in self.cache:
return -1
node = self.cache[key]
self._remove_node(node)
self._add_to_head(node)
return node.value
def put(self, key: int, value: int) -> None:
if key in self.cache:
node = self.cache[key]
node.value = value
self._remove_node(node)
self._add_to_head(node)
else:
new_node = self.Node(key, value)
self.cache[key] = new_node
self._add_to_head(new_node)
if len(self.cache) > self.capacity:
lru_node = self.tail.prev
self._remove_node(lru_node)
del self.cache[lru_node.key]
```mistral-small-3.1-24b-instruct-2503 · baseline · PASS
```python
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity: int):
self.cache = OrderedDict()
self.capacity = capacity
def get(self, key: int) -> int:
if key not in self.cache:
return -1
else:
self.cache.move_to_end(key)
return self.cache[key]
def put(self, key: int, value: int) -> None:
if key in self.cache:
self.cache.move_to_end(key)
self.cache[key] = value
if len(self.cache) > self.capacity:
self.cache.popitem(last=False)
```qwen3.5-122b-a10b-cluster · baseline · PASS
```python
class LRUCache:
class Node:
def __init__(self, key, value):
self.key = key
self.value = value
self.prev = None
self.next = None
def __init__(self, capacity: int):
self.capacity = capacity
self.cache = {}
self.size = 0
# Dummy head and tail nodes to simplify edge cases
self.head = self.Node(0, 0)
self.tail = self.Node(0, 0)
self.head.next = self.tail
self.tail.prev = self.head
def _add_to_head(self, node):
node.prev = self.head
node.next = self.head.next
self.head.next.prev = node
self.head.next = node
def _remove_node(self, node):
prev = node.prev
next = node.next
prev.next = next
next.prev = prev
def _move_to_head(self, node):
self._remove_node(node)
self._add_to_head(node)
def _pop_tail(self):
res = self.tail.prev
self._remove_node(res)
return res
def get(self, key):
node = self.cache.get(key)
if not node:
return -1
self._move_to_head(node)
return node.value
def put(self, key, value):
node = self.cache.get(key)
if node:
node.value = value
self._move_to_head(node)
else:
new_node = self.Node(key, value)
self.cache[key] = new_node
self._add_to_head(new_node)
self.size += 1
if self.size > self.capacity:
tail = self._pop_tail()
del self.cache[tail.key]
self.size -= 1
```gpt-oss-20b · baseline · PASS
```python
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity: int):
if capacity <= 0:
raise ValueError("Capacity must be a positive integer")
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key: int) -> int:
if key not in self.cache:
return -1
value = self.cache.pop(key)
self.cache[key] = value # reinsert to mark as most recent
return value
def put(self, key: int, value: int) -> None:
if key in self.cache:
self.cache.pop(key)
elif len(self.cache) >= self.capacity:
self.cache.popitem(last=False) # remove least recently used
self.cache[key] = value
```qwen3-coder-30b · baseline · PASS
```python
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity):
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key):
if key not in self.cache:
return -1
# Move to end to mark as recently used
self.cache.move_to_end(key)
return self.cache[key]
def put(self, key, value):
if key in self.cache:
# Update existing key
self.cache.move_to_end(key)
elif len(self.cache) >= self.capacity:
# Remove least recently used (first item)
self.cache.popitem(last=False)
self.cache[key] = value
```gemma-4-26b-a4b-it · baseline · PASS
```python
from collections import OrderedDict
class LRUCache:
"""
An implementation of an LRU (Least Recently Used) Cache.
Uses collections.OrderedDict to maintain O(1) time complexity for
both get and put operations by leveraging its doubly linked list
and hash map internal structure.
"""
def __init__(self, capacity: int):
"""
Initialize the LRUCache with a positive integer capacity.
"""
if capacity <= 0:
raise ValueError("Capacity must be a positive integer.")
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key: int) -> int:
"""
Return the value of the key if it exists, otherwise return -1.
Accessing a key moves it to the end (most recent position).
"""
if key not in self.cache:
return -1
# Move the accessed key to the end to mark it as most recently used
self.cache.move_to_end(key)
return self.cache[key]
def put(self, key: int, value: int) -> None:
"""
Insert or update the value for the given key.
If the capacity is exceeded, evict the least recently used entry.
"""
if key in self.cache:
# Update existing key and move to end
self.cache.move_to_end(key)
self.cache[key] = value
if len(self.cache) > self.capacity:
# popitem(last=False) removes the first item (the least recently used)
self.cache.popitem(last=False)
```qwen3.6-35b-a3b-or · baseline · PASS
```python
class Node:
def __init__(self, key=0, value=0):
self.key = key
self.value = value
self.prev = None
self.next = None
class LRUCache:
def __init__(self, capacity):
self.capacity = capacity
self.cache = {}
# Initialize dummy head and tail nodes
self.head = Node()
self.tail = Node()
self.head.next = self.tail
self.tail.prev = self.head
def _add_to_head(self, node):
node.prev = self.head
node.next = self.head.next
self.head.next.prev = node
self.head.next = node
def _remove_node(self, node):
node.prev.next = node.next
node.next.prev = node.prev
def _move_to_head(self, node):
self._remove_node(node)
self._add_to_head(node)
def _pop_tail(self):
res = self.tail.prev
self._remove_node(res)
return res
def get(self, key):
if key in self.cache:
node = self.cache[key]
self._move_to_head(node)
return node.value
return -1
def put(self, key, value):
if key in self.cache:
node = self.cache[key]
node.value = value
self._move_to_head(node)
else:
new_node = Node(key, value)
self.cache[key] = new_node
self._add_to_head(new_node)
if len(self.cache) > self.capacity:
tail_node = self._pop_tail()
del self.cache[tail_node.key]
```gemini-2.5-flash-lite · baseline · PASS
```python
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
self.cache = {}
self.order = []
def get(self, key: int) -> int:
if key not in self.cache:
return -1
else:
self.order.remove(key)
self.order.append(key)
return self.cache[key]
def put(self, key: int, value: int) -> None:
if key in self.cache:
self.cache[key] = value
self.order.remove(key)
self.order.append(key)
else:
if len(self.cache) >= self.capacity:
lru_key = self.order.pop(0)
del self.cache[lru_key]
self.cache[key] = value
self.order.append(key)
```qwen3.6-35b-bf16 · baseline · PASS
```python
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity):
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key):
if key in self.cache:
self.cache.move_to_end(key)
return self.cache[key]
return -1
def put(self, key, value):
if key in self.cache:
self.cache.move_to_end(key)
elif len(self.cache) >= self.capacity:
self.cache.popitem(last=False)
self.cache[key] = value
```granite-4.1-30b · baseline · PASS
```python
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity: int):
if capacity <= 0:
raise ValueError("Capacity must be a positive integer")
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key: int) -> int:
if key not in self.cache:
return -1
# Move the accessed key to the end to mark it as recently used
self.cache.move_to_end(key)
return self.cache[key]
def put(self, key: int, value: int) -> None:
if key in self.cache:
# Update the value and move it to the end (most recent)
self.cache.move_to_end(key)
self.cache[key] = value
if len(self.cache) > self.capacity:
# Pop the first item (least recently used)
self.cache.popitem(last=False)
```qwen3.6-27b · v1.7.1 · PASS
```python
class Node:
def __init__(self, key=0, value=0):
self.key = key
self.value = value
self.prev = None
self.next = None
class DoublyLinkedList:
def __init__(self):
# Sentinel nodes to simplify edge cases
self.head = Node()
self.tail = Node()
self.head.next = self.tail
self.tail.prev = self.head
def add_to_front(self, node):
"""Add a node right after the head (most recently used position)."""
node.prev = self.head
node.next = self.head.next
self.head.next.prev = node
self.head.next = node
def remove_node(self, node):
"""Remove an existing node from the list."""
prev_node = node.prev
next_node = node.next
prev_node.next = next_node
next_node.prev = prev_node
def remove_last(self):
"""Remove and return the node just before the tail (least recently used)."""
if self.head.next == self.tail:
return None
lru_node = self.tail.prev
self.remove_node(lru_node)
return lru_node
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
self.cache_map = {} # key -> Node
self.dll = DoublyLinkedList()
def get(self, key: int) -> int:
if key not in self.cache_map:
return -1
node = self.cache_map[key]
# Move accessed node to front (most recently used)
self.dll.remove_node(node)
self.dll.add_to_front(node)
return node.value
def put(self, key: int, value: int) -> None:
if key in self.cache_map:
# Update existing key
node = self.cache_map[key]
node.value = value
# Move to front (most recently used)
self.dll.remove_node(node)
self.dll.add_to_front(node)
else:
# Insert new key
if len(self.cache_map) >= self.capacity:
# Evict least recently used
lru_node = self.dll.remove_last()
if lru_node:
del self.cache_map[lru_node.key]
# Add new node
new_node = Node(key, value)
self.cache_map[key] = new_node
self.dll.add_to_front(new_node)
```qwen3-next-80b · baseline · PASS
```python
class LRUCache:
def __init__(self, capacity):
self.capacity = capacity
self.cache = {}
self.order = []
def get(self, key):
if key not in self.cache:
return -1
# Move the accessed key to the end (most recently used)
self.order.remove(key)
self.order.append(key)
return self.cache[key]
def put(self, key, value):
if key in self.cache:
# Update existing key and move to end
self.cache[key] = value
self.order.remove(key)
self.order.append(key)
else:
# Add new key-value pair
if len(self.cache) >= self.capacity:
# Evict least recently used (first in order list)
lru_key = self.order.pop(0)
del self.cache[lru_key]
self.cache[key] = value
self.order.append(key)
```qwen3.5-4b · baseline · PASS
```python
class LRUCache:
def __init__(self, capacity):
self.capacity = capacity
self.cache = {} # key -> value mapping
self.order = [] # list to track order of usage (most recent at end)
def get(self, key):
if key not in self.cache:
return -1
# Move key to end (most recently used)
self.order.remove(key)
self.order.append(key)
return self.cache[key]
def put(self, key, value):
if key in self.cache:
# Update existing key
self.order.remove(key)
self.order.append(key)
self.cache[key] = value
else:
# Add new key
self.order.append(key)
self.cache[key] = value
# If exceeds capacity, evict least recently used (first in order list)
if len(self.cache) > self.capacity:
lru_key = self.order.pop(0)
del self.cache[lru_key]
```phi-4-reasoning-plus · baseline · PASS
We are asked: "Implement a class `LRUCache` with:
- __init__(self, capacity) - positive int capacity
- get(self, key) - return the value, or -1 if the key is absent
- put(self, key, value) - insert/update
When inserting would exceed capacity, evict the LEAST-recently-used entry. Both `get` and `put` on a key count as using it (refresh its recency). Importable as `from solution import LRUCache`."
We need to produce a single self-contained Python solution in one code block with no explanation before or after.
I'll produce a python file that defines the class. We can use collections.OrderedDict, but note that Python 3.7+ dict preserves insertion order, but we want LRU ordering. But it's easier to implement using OrderedDict from collections module. Alternatively, we can implement our own doubly linked list with dictionary mapping keys to nodes.
I'll produce a solution using OrderedDict because it's simpler and built-in. However, note that the problem says "importable as `from solution import LRUCache`", so I need to define a file named solution.py? But instructions say: "Output a single self-contained Python solution as one ```python code block" with no explanation before or after.
I'll produce a python code block containing the class definition. We can use collections.OrderedDict. The typical approach is:
```
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key: int) -> int:
if key not in self.cache:
return -1
value = self.cache.pop(key)
self.cache[key] = value # reinsert to mark as recently used.
return value
def put(self, key: int, value: int) -> None:
if key in self.cache:
self.cache.pop(key)
elif len(self.cache) >= self.capacity:
self.cache.popitem(last=False) # pop least recently used
self.cache[key] = value
```
That is the simplest solution.
I'll produce a code block with triple backticks and "python" language marker. I must not include any explanation before or after, so I'll just output the code block.
I'll produce a code block that includes the class definition and then if __name__ == '__main__': maybe some tests? But instructions say "self-contained solution", but it's ambiguous whether we need to include test cases. The problem says "Implement a class LRUCache" with methods get, put etc. It doesn't require main function or tests.
I can produce the code block that defines the class and then if __name__ == '__main__': maybe some sample usage? But instructions say "importable as from solution import LRUCache", so I'll not include a main test harness because it's supposed to be imported. But I might include a simple demonstration in a comment.
I can produce code block with the class definition and then if __name__ == '__main__': maybe some tests? The instructions say "self-contained Python solution" but also "importable as from solution import LRUCache". So it's ambiguous whether to include main test harness. I'll produce a file that defines the class, and optionally add a main block with sample usage commented out.
I can produce code block:
```
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity: int):
if capacity <= 0:
raise ValueError("Capacity must be positive")
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key) -> int:
if key not in self.cache:
return -1
# Move the key to end to show that it was recently used.
value = self.cache.pop(key)
self.cache[key] = value
return value
def put(self, key, value):
if key in self.cache:
# Remove old
self.cache.pop(key)
elif len(self.cache) >= self.capacity:
# Pop least recently used item.
self.cache.popitem(last=False)
self.cache[key] = value
```
I'll produce that code block. I must not include any explanation before or after.
I'll produce a single python code block with the class definition and maybe some tests if needed? But instructions say "self-contained solution", so it's better to include main test harness if possible, but then it might conflict with importable as from solution import LRUCache. I can include a main block that is guarded by if __name__ == '__main__': which runs sample usage.
I'll produce code block:
```
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity: int):
if capacity <= 0:
raise ValueError("Capacity must be positive")
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key) -> int:
if key not in self.cache:
return -1
# Move the key to end to mark it as recently used.
value = self.cache.pop(key)
self.cache[key] = value
return value
def put(self, key, value):
if key in self.cache:
self.cache.pop(key)
elif len(self.cache) >= self.capacity:
self.cache.popitem(last=False)
self.cache[key] = value
if __name__ == '__main__':
# Example usage:
cache = LRUCache(2)
cache.put(1, 1)
cache.put(2, 2)
print(cache.get(1)) # returns 1
cache.put(3, 3) # evicts key 2
print(cache.get(2)) # returns -1 (not found)
cache.put(4, 4) # evicts key 1
print(cache.get(1)) # returns -1 (not found)
print(cache.get(3)) # returns 3
print(cache.get(4)) # returns 4
```
I'll produce that code block. But instructions say "self-contained solution" and "importable as from solution import LRUCache". So I must not include any explanation before or after, but it's allowed to have a main block if __name__ == '__main__' because then the file can be imported.
But instructions said: "Output a single seldeepseek-r1-distill-qwen-32b · baseline · PASS
To solve this problem, we need to implement an LRUCache (Least Recently Used Cache) class that efficiently manages a cache with a specified capacity. The cache should support getting and putting key-value pairs while evicting the least recently used entry when the capacity is exceeded.
### Approach
The approach involves using an `OrderedDict` from Python's `collections` module, which maintains the insertion order of elements. This allows us to efficiently track the most and least recently used entries. Here’s a detailed breakdown:
1. **Initialization**: The cache is initialized with a given positive integer capacity. An `OrderedDict` is used to store the key-value pairs.
2. **Get Operation**: When retrieving a value using a key, if the key exists, it is moved to the end of the dictionary to mark it as recently used. If the key does not exist, -1 is returned.
3. **Put Operation**: When inserting or updating a key-value pair, if the key already exists, its value is updated and the entry is moved to the end. If the key does not exist, it is added to the end of the dictionary. After adding, if the cache exceeds its capacity, the least recently used entry (the first item in the dictionary) is removed.
### Solution Code
```python
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity):
self.cache = OrderedDict()
self.capacity = capacity
def get(self, key):
if key not in self.cache:
return -1
# Move the accessed key to the end to mark it as recently used
self.cache.move_to_end(key)
return self.cache[key]
def put(self, key, value):
if key in self.cache:
# Update the value and move the key to the end
self.cache[key] = value
self.cache.move_to_end(key)
else:
# Add new entry at the end
self.cache[key] = value
# Check if we need to evict the least recently used item
if len(self.cache) > self.capacity:
self.cache.popitem(last=False) # Remove from the beginning (least recently used)
```
### Explanation
- **Initialization**: The constructor initializes an `OrderedDict` and sets the cache capacity.
- **Get Method**: Checks if the key exists. If it does, the key is moved to the end of the dictionary to update its recency, and the value is returned. If not found, -1 is returned.
- **Put Method**: Updates or adds a key-value pair. After adding, if the cache exceeds capacity, the least recently used entry (the first item) is removed.
This approach ensures that both get and put operations are efficient, with average time complexity of O(1), making it suitable for scenarios where frequent cache operations are expected.qwen3.6-35b-a3b · baseline · PASS
```python
class Node:
def __init__(self, key=0, value=0):
self.key = key
self.value = value
self.prev = None
self.next = None
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
self.cache = {} # key -> Node
# Dummy head and tail nodes
self.head = Node() # Most recently used end
self.tail = Node() # Least recently used end
self.head.next = self.tail
self.tail.prev = self.head
def _add_to_head(self, node: Node):
"""Add a node right after the head (most recent position)."""
node.prev = self.head
node.next = self.head.next
self.head.next.prev = node
self.head.next = node
def _remove_node(self, node: Node):
"""Remove a node from its current position."""
prev_node = node.prev
next_node = node.next
prev_node.next = next_node
next_node.prev = prev_node
def _move_to_head(self, node: Node):
"""Move an existing node to the head (most recent)."""
self._remove_node(node)
self._add_to_head(node)
def _pop_tail(self) -> Node:
"""Remove and return the node just before the tail (least recent)."""
node = self.tail.prev
self._remove_node(node)
return node
def get(self, key: int) -> int:
if key not in self.cache:
return -1
node = self.cache[key]
self._move_to_head(node)
return node.value
def put(self, key: int, value: int) -> None:
if key in self.cache:
node = self.cache[key]
node.value = value
self._move_to_head(node)
else:
if len(self.cache) >= self.capacity:
# Evict the least recently used item (just before tail)
lru_node = self._pop_tail()
del self.cache[lru_node.key]
new_node = Node(key, value)
self.cache[key] = new_node
self._add_to_head(new_node)
```qwen3.6-27b · baseline · PASS
```python
class Node:
def __init__(self, key=0, value=0):
self.key = key
self.value = value
self.prev = None
self.next = None
class DoublyLinkedList:
def __init__(self):
# Sentinel nodes to simplify edge cases
self.head = Node()
self.tail = Node()
self.head.next = self.tail
self.tail.prev = self.head
def add_to_front(self, node):
"""Add a node right after the head (most recently used position)."""
node.prev = self.head
node.next = self.head.next
self.head.next.prev = node
self.head.next = node
def remove_node(self, node):
"""Remove an existing node from the list."""
prev_node = node.prev
next_node = node.next
prev_node.next = next_node
next_node.prev = prev_node
def remove_last(self):
"""Remove and return the node just before the tail (least recently used)."""
if self.head.next == self.tail:
return None
lru_node = self.tail.prev
self.remove_node(lru_node)
return lru_node
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
self.cache_map = {} # key -> Node
self.dll = DoublyLinkedList()
def get(self, key: int) -> int:
if key not in self.cache_map:
return -1
node = self.cache_map[key]
# Move accessed node to front (most recently used)
self.dll.remove_node(node)
self.dll.add_to_front(node)
return node.value
def put(self, key: int, value: int) -> None:
if key in self.cache_map:
# Update existing key
node = self.cache_map[key]
node.value = value
# Move to front (most recently used)
self.dll.remove_node(node)
self.dll.add_to_front(node)
else:
# Insert new key
if len(self.cache_map) >= self.capacity:
# Evict least recently used
lru_node = self.dll.remove_last()
if lru_node:
del self.cache_map[lru_node.key]
# Add new node
new_node = Node(key, value)
self.cache_map[key] = new_node
self.dll.add_to_front(new_node)
```claude-sonnet-4.6 · baseline · PASS
```python
from collections import OrderedDict
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
self.cache = OrderedDict()
def get(self, key: int) -> int:
if key not in self.cache:
return -1
self.cache.move_to_end(key)
return self.cache[key]
def put(self, key: int, value: int) -> None:
if key in self.cache:
self.cache.move_to_end(key)
self.cache[key] = value
else:
if len(self.cache) >= self.capacity:
self.cache.popitem(last=False)
self.cache[key] = value
```qwen3.5-4b · bare · fail
```python
class LRUCache:
def __init__(self, capacity):
self.capacity = capacity
self.cache = {} # key -> value mapping
self.head = Node(None)
self.tail = Node(None)
self.head.next = self.tail
self.tail.prev = self.head
class Node:
def __init__(self, key=None, value=None):
self.key = key
self.value = value
self.prev = None
self.next = None
def _move_to_end(self, node):
"""Move a node to the end (most recently used)"""
if node == self.tail:
return
node.prev.next = node.next
if node.next:
node.next.prev = node.prev
node.next = self.tail
node.prev = self.tail.prev
self.tail.prev = node
node.next.prev = node
def _remove(self, node):
"""Remove a node from the list"""
node.prev.next = node.next
if node.next:
node.next.prev = node.prev
def get(self, key):
if key not in self.cache:
return -1
node = self.cache[key]
self._move_to_end(node)
return node.value
def put(self, key, value):
if key in self.cache:
node = self.cache[key]
node.value = value
self._move_to_end(node)
else:
node = Node(key, value)
self.cache[key] = node
self._add_to_end(node)
if len(self.cache) > self.capacity:
lru_node = self.head.next
self._remove(lru_node)
del self.cache[lru_node.key]
def _add_to_end(self, node):
"""Add a node to the end (most recently used)"""
node.prev = self.tail.prev
node.next = self.tail
self.tail.prev.next = node
self.tail.prev = node
```qwen3.5-2b · baseline · fail
```python
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
# Map from key to value and a doubly-linked list node for LRU order
self.cache = {}
self.head = None # Head of the doubly linked list (most recently used)
self.tail = None # Tail of the doubly linked list
def _add_to_head(self, key: int):
"""Add a new entry to the head of the LRU list."""
node = {'key': key, 'value': None}
if not self.head:
self.head = self.tail = node
else:
# Remove from current tail position (if exists)
prev_tail = self.tail
if prev_tail and prev_tail['key'] == key:
prev_tail = None
# Insert at head
node['next'] = self.head
self.head['prev'] = node
self.head = node
self.cache[key] = node
def _remove_from_list(self, key: int):
"""Remove a node from the doubly linked list."""
if key in self.cache:
node = self.cache[key]
prev_tail = node['prev']
next_node = node['next']
if prev_tail:
prev_tail['next'] = next_node
else:
# This is the head, remove it entirely
self.head = next_node
if next_node:
next_node['prev'] = prev_tail
del self.cache[key]
def get(self, key: int) -> int:
"""Return value of key or -1 if absent."""
if key not in self.cache:
return -1
node = self.cache[key]
# Move to head (mark as most recently used)
self._add_to_head(key)
return node['value']
def put(self, key: int, value: int):
"""Insert or update key-value pair. Evict LRU if capacity exceeded."""
if key in self.cache:
# Update existing entry
self.cache[key]['value'] = value
self._add_to_head(key) # Refresh recency
else:
# Check capacity and evict if needed
if len(self.cache) >= self.capacity:
lru_key = self.head['key']
del self.cache[lru_key]
self._remove_from_list(lru_key)
# Insert new entry at head
node = {'key': key, 'value': value}
if not self.head:
self.head = self.tail = node
else:
prev_tail = self.tail
if prev_tail and prev_tail['key'] == key:
prev_tail = None
node['next'] = self.head
self.head['prev'] = node
self.head = node
self.cache[key] = node
```qwen3.5-0.8b · baseline · fail
```python
class LRUCache:
"""A cache that keeps at most 'capacity' entries, with the least-recently-used entry evicted."""
def __init__(self, capacity: int):
self.capacity = capacity
self.cache: dict[str, tuple[int, str]] = {} # key -> (value, recency)
self.recent_keys: set[str] = set() # keys that have been recently accessed
def _get_key(self, key: str) -> int | None:
"""Get the index of a key in the cache. Returns -1 if not found."""
return self.cache.get(key)
def _evict_least_recently_used(self):
"""Remove the least-recently-used entry from the cache and its associated keys."""
# Find the last element (most recently used)
last_key = max(self.recent_keys, key=len) if self.recent_keys else None
if not last_key:
return
# Remove this key and all its entries
del self.cache[last_key]
for k in self.recent_keys:
self.recent_keys.discard(k)
def _update_relevance(self, key: str):
"""Update the recency of a key."""
if key not in self.cache:
return
value, _ = self.cache[key]
# Update recency by incrementing it (or keeping as is for simplicity)
self.recent_keys.add(key)
def get(self, key: str) -> int | None:
"""Return the value of a key, or -1 if not found."""
idx = self._get_key(key)
if idx is not None and idx in self.cache:
return self.cache[idx][0]
return None
def put(self, key: str, value: int):
"""Insert/update a key-value pair. If capacity exceeded, evict least-recently-used."""
# Check if we can insert this key
idx = self._get_key(key)
if idx is not None and idx in self.cache:
return # Already exists
# Insert the new entry
self.cache[key] = (value, len(self.recent_keys))
self._update_relevance(key)
# Check capacity
if len(self.cache) > self.capacity:
self._evict_least_recently_used()
```