LeetCode | Two Sum

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) {    int res1 = 0, res2 = 0;    multimap<int,int> m;    multimap<int,int>::iterator it;    multimap<int,int>::iterator it2;    vector<int> res;    for(int i=0;i<nums.size();i++)    {        m.insert(make_pair(nums[i],i));    }    it2 = m.begin();    for(int i=0;i<nums.size();i++)    {        if(it2->first > target/2)            break;        it = m.find(target-it2->first);        if(it!=m.end() && it!=it2)        {            res1 = it->second;            res2 = it2->second;            break;        }        it2++;    }    if(res1 > res2)        swap(res1,res2);    res.push_back(res1);    res.push_back(res2);    return res;    }};