LeetCode-1. 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) {
        
        unordered_map<int,int> m;
        vector<int> ret;
        
        for(int i=0;i<nums.size();i++)
            m[nums[i]] = i;
        
        for(int i=0;i<nums.size();i++)
        {
            int complement = target - nums[i];
            
            if(m.count(complement) && m[complement] != i)
            {
                ret.push_back(i);
                ret.push_back(m[complement]);
                break;
            }
        }
        return ret;
        
    }
};