LRU Cache--LeetCode

Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set.

get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.

set(key, value) - Set or insert the value if the key is not already present. When the cache reached its capacity, it should invalidate the least recently used item before inserting a new item.

这里直接用JS中的Map数据结构。Map是有顺序的，后加的在在后面。JS中的Map应该不是Hash_Map(unordered_map)，应该是TreeMap(红黑树)，因为它是有顺序。用Array会超时。这道题用JS实现没啥含量，数据结构不是自己写的。不过ES6的Map确实很有用。在LeetCode上，比很多的语言快。

var LRUCache = function(capacity) {
    this.size=capacity;
    this.map=new Map();

};
LRUCache.prototype.get = function(key) {
    var value= this.map.get(key);

    if(value===undefined){return -1;}else{
        this.map.delete(key)
        this.map.set(key,value)
        return value;
    }
};
LRUCache.prototype.set = function(key, value) {
    if(this.map.has(key)){
        this.map.delete(key)
    }

    this.map.set(key, value);
    if(this.map.size>this.size){
        for(var x of this.map.keys()){
            this.map.delete(x);
            return;
        }
    }
}//Runtime: 200 ms  94.12%