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0146-lru-cache/README.md

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+<h2><a href="https://leetcode.com/problems/lru-cache/">146. LRU Cachea>h2><h3>Mediumh3><hr><p>Design a data structure that follows the constraints of a <strong><a href="https://en.wikipedia.org/wiki/Cache_replacement_policies#LRU" target="_blank">Least Recently Used (LRU) cachea>strong>.p>
+
+<p>Implement the <code>LRUCachecode> class:p>
+
+<ul>
+	LRUCache(int capacity) Initialize the LRU cache with positive size capacity.
+	int get(int key) Return the value of the key 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 the key-value pair to the cache. If the number of keys exceeds the capacity from this operation, evict the least recently used key.
+ul>
+
+<p>The functions <code>getcode> and <code>putcode> must each run in <code>O(1)code> average time complexity.p>
+
+<p>&nbsp;p>
+<p><strong class="example">Example 1:strong>p>
+
+<pre>
+<strong>Inputstrong>
+[&quot;LRUCache&quot;, &quot;put&quot;, &quot;put&quot;, &quot;get&quot;, &quot;put&quot;, &quot;get&quot;, &quot;put&quot;, &quot;get&quot;, &quot;get&quot;, &quot;get&quot;]
+[[2], [1, 1], [2, 2], [1], [3, 3], [2], [4, 4], [1], [3], [4]]
+<strong>Outputstrong>
+[null, null, null, 1, null, -1, null, -1, 3, 4]
+
+<strong>Explanationstrong>
+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
+pre>
+
+<p>&nbsp;p>
+<p><strong>Constraints:strong>p>
+
+<ul>
+	1 <= capacity <= 3000
+	0 <= key <= 104
+	0 <= value <= 105
+	At most 2 * 105 calls will be made to get and put.
+ul>