leetcode-【简单题】Two Sum

题目：

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.

样例：

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

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

答案：

简单遍历vector就行了，size*size复杂度，本来想先排序，再遍历，但是排序需要记录排序前和排序后索引的对应关系。

代码：

#include <algorithm>

class Solution {
private:
   static bool cmp(const int &a, const int &b)
   {
       return a < b;
   }
   
public:
    vector<int> twoSum(vector<int>& nums, int target) {
       // std::sort(nums.begin(),nums.end(),cmp);
        
        int i,j;
        int size = nums.size();
        int rest;
        vector<int> ans;
        
        for(i = 0; i < size; ++ i)
        {
            rest = target - nums[i];
            for(j = i + 1;j < size; ++ j)
            {
                if(rest == nums[j])
                {
                    ans.push_back(i);
                    ans.push_back(j);
                    return ans;
                }
            }
        }
    }
};