lleetcode 1 two sum c++

Problem describe:https://leetcode.com/problems/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.

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

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

AC code :

1.Bruth Algorithm

 class Solution {
 public:
     vector<int> twoSum(vector<int>& nums, int target) {
         vector<int> res;
         for(int i = ;i < nums.size();i++)
             for(int j = i + ;j < nums.size();j++)
                 if(nums[i]+nums[j]==target)
                 {
                     res.push_back(i);
                     res.push_back(j);
                 }
         return res;

     }
 };

2.Hashmap

 class Solution {
 public:
     vector<int> twoSum(vector<int>& nums, int target) {
         vector<int> res;
         unordered_map<int,int> map;
         for(int i = ; i < nums.size();i++)
         {
             map[nums[i]] = i;
         }
         for(int i = ;i < nums.size();i++)
         {
             int left = target - nums[i];
             if(map.count(left) && i <  map[left])
             {
                 res.push_back(i);
                 res.push_back(map[left]);
             }
         }
         return res;
     }
 };