LC 1. 两数之和

代码 :

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        unordered_map<int, int> hash; 
        for(int i = 0; i < nums.size(); i ++ ) {
            int s = nums[i];
            if(hash.count(target - s)) {
                int index = hash[target - s];
                return {index, i};
            }
            hash[s] = i;
        }
        return {-1, -1};
    }
};