Leetcode 1. Two Sum(hash+stl)

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        vector<int> tm;
        int a = 0, b = 0;
        int len = nums.size();
        
        multimap<int,int> hash;
        
        for(int i = 0; i < len; i++){
            hash.insert(pair<int,int>(nums[i],i));
        }
        for(int i = 0; i < len; i++){
            multimap<int,int>::iterator s;
            s=hash.find(target-nums[i]);
            if(s== hash.end()){
                continue;
            }
            if(i != (*s).second){
                a = i;
                b = (*s).second;
                break;
            }
        }
        tm.push_back(a);
        tm.push_back(b);
        return tm;
    }
};