leetcode-华为专题-1. 两数之和

 

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        vector<int> res;
        unordered_map<int,int> un_map;

        for(int i = 0; i < nums.size(); i++){
            if(un_map.find(target-nums[i]) != un_map.end()){ // 判断是否存在
                res.push_back(un_map[target-nums[i]]);
                res.push_back(i);
                return res;
            }
            un_map[nums[i]]=i; // 经当前元素以及下标作为key -value
        }

        return res;
    }
};