LeetCode 1. 两数之和

https://leetcodechina.com/problems/two-sum/description/
map

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        vector<int> ans;
        map<int, int> vis;
        for (int i = 0; i < nums.size(); ++i){
            if (!vis.count(nums[i])) vis[target - nums[i]] = i;
            else  ans.push_back(vis[nums[i]]),ans.push_back(i);
        }
        return ans;
    }
};