转专业beginner刷题贴

Graduated. Not job. Beginner. 谢谢大家监督。

1. Two Sum

1.      class Solution {
   
2.      public:
   
3.          vector<int> twoSum(vector<int>& nums, int target) {
   
4.              unordered_map<int, int> mp;
   
5.              for(int i=0; i<nums.size(); i++){
   
6.                  auto iter = mp.find(target-nums[i]);
   
7.                  if (iter == mp.end())
   
8.                      mp[nums[i]] = i;
   
9.                  else{
   
10.                      return {iter->second, i};
    
11.                  }
    
12.              }
    
13.          }
    
14.      };

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好心人帮我加点分，很多东西看不了

Next Permutation:  find the index where it and all its right are in descending order (use a for loop), update its left element by finding from its right the element right greater it.

Permutations: backtracking

Combination: backtracking

Add Two Numbers