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;

     }

 };

巴特西

lleetcode 1 two sum c++

AC code :

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