LeetCode兩數之和

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]

大意爲，給定一個數組，和一個目標值，要求從數組中選出兩個數字之和等於目標值，返回兩個值在數組中的下標。

class Solution {
public:
    int sum;
    vector<int> twoSum(vector<int>& nums, int target) {
    	int sum = target;
    	vector<int> out;
    	int a, b;
          for (int i = 0; i < nums.size();i++ ) {
          	target = sum;
          	target-=nums[i];
          	a = i;
          	for (int j = i+1; j < nums.size(); j++) {
          		if(target == nums[j]) {
          			b = j;
          			out.push_back(a);
          			out.push_back(b);
          			return out;
					}
				}
		  }
        return out;
    }
};

暴力求解，速度是C++提交中的50%。