Design a data structure that follows the constraints of a Least Recently Used (LRU) cache
Implement the LRUCache
class:
LRUCache(int capacity)
Initialize the LRU cache with a positive sizecapacity
.int get(int key)
Return the value of thekey
if the key exists, otherwise return-1
.void put(int key, int value)
Update the value of the key if the key exists. Otherwise, add thekey-value
pair to the cache. If the number of keys exceeds thecapacity
from this operation, evict the least recently used key.
Example:
Input
["LRUCache", "put", "put", "get", "put", "get", "put", "get", "get", "get"]
[[2], [1, 1], [2, 2], [1], [3, 3], [2], [4, 4], [1], [3], [4]]
Output
[null, null, null, 1, null, -1, null, -1, 3, 4]
Explanation
LRUCache lRUCache = new LRUCache(2);
lRUCache.put(1, 1); // cache is {1=1}
lRUCache.put(2, 2); // cache is {1=1, 2=2}
lRUCache.get(1); // return 1
lRUCache.put(3, 3); // LRU key was 2, evicts key 2, cache is {1=1, 3=3}
lRUCache.get(2); // returns -1 (not found)
lRUCache.put(4, 4); // LRU key was 1, evicts key 1, cache is {4=4, 3=3}
lRUCache.get(1); // return -1 (not found)
lRUCache.get(3); // return 3
lRUCache.get(4); // return 4
Approach:
C++
#include <bits/stdc++.h>using namespace std;class LRUCache{public:int cap;vector<int> v;unordered_map<int, int> mp;LRUCache(int capacity){cap = capacity;}int get(int key){auto pos = find(v.begin(), v.end(), key);if (pos != v.end()){v.erase(pos);v.push_back(key);return mp[key];}return -1;}void put(int key, int value){auto pos = find(v.begin(), v.end(), key);if (pos != v.end())v.erase(pos);if (v.size() == cap){mp[v[0]] = 0;v.erase(v.begin());}mp[key] = value;v.push_back(key);}};int main(){LRUCache lRUCache(2);lRUCache.put(1, 1);lRUCache.put(2, 2);cout << "[";cout << lRUCache.get(1) << ", ";lRUCache.put(3, 3);cout << lRUCache.get(2) << ", ";lRUCache.put(4, 4);cout << lRUCache.get(1) << ", ";cout << lRUCache.get(3) << ", ";cout << lRUCache.get(4);cout << "]";return 0;}
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