Given an array of integers, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution.

Input: numbers={2, 7, 11, 15}, target=9

Output: index1=1, index2=2

题意：给你一个数组，告诉你有唯一解是两个数相加等于target，求下标分别是多少

思路：map离散储存，相对简单的一道题

class Solution {
public:
    vector<int> twoSum(vector<int> &numbers, int target) {
        vector<int> ans;
        map<int, int> mp;
        for (int i = 0; i < numbers.size(); i++) {
            int tmp = target - numbers[i];
            if (mp.find(tmp) != mp.end()) {
                ans.push_back(mp[tmp]);
                ans.push_back(i+1);
            }
            else mp[numbers[i]] = i+1;
        }
        return ans;
    }
};

LeetCode Two Sum