1. 两数之和

[zpc7]

1. 两数之和

// 暴力循环破解 O(n2)
var twoSum = function (nums, target) {
    for (let i = 0; i < nums.length; i++) {
        for (let j = i + 1; j < nums.length; j++) {
            if (nums[i] + nums[j] === target) {
                return [i, j]
            }
        }
    }
};
// 借助 map O(n)
var twoSum = function (nums, target) {
  const map = {}
  for (let i = 0; i < nums.length; i++) {
    const anthorItem = target - nums[i];
    if (map[anthorItem] !== undefined) {
      return [i, map[anthorItem]];
    } else {
      map[nums[i]] = i;
    }
  }
}