算法记录—两数之和

开始刷算法题了 先从简单的开始吧 抵制emo最好的方法就是行动！
用例如下：

输入：nums = [2,7,11,15], target = 9
输出：[0,1]
解释：因为 nums[0] + nums[1] == 9 ，返回 [0, 1] 。

1.简单粗暴双循环 时间复杂度O(n2)：

// @lc code=start

var twoSum = function (nums, target) {
    let map = new Map()
    
    for (let i = 0; i < nums.length; i++) { 
        for (let j = i+1; j < nums.length; j++) { 
            let sum=nums[i]+nums[j]
            if (sum == target) { 
                return [i,j]
            }
        }
    }
};

Your runtime beats 46.07 % of javascript submissions
Your memory usage beats 74.31 % of javascript submissions (38.6 MB)

2.哈希-相减寻值-时间复杂度O(n)

//知识点记录下--Map
//创建Map
let map = new Map()
//塞值
map.set(key,value)
//取值
map.get(key)
///判断Key值是否存在
map.has(key)
//删除key
map.delete(key)

题解记录：

// @lc code=start

var twoSum = function (nums, target) {
    let maps = new Map();
  for (let i = 0; i < nums.length; i++) {
    const temp = target - nums[i];
    if (maps.has(temp) && i !== maps.get(temp)) {
      return [i, maps.get(temp)];
    }
    maps.set(nums[i], i);
  }
};

Your runtime beats 87.61 % of javascript submissions
Your memory usage beats 8.48 % of javascript submissions (40.6 MB)