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.

Example:

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

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

分析

这道题借用STL中的map结构求解比较简单

声明一个int到int的map用于将数组中的数及其下标联系起来

遍历一遍数组

如果target减去当前元素存在于map中，则将当前下标i和map[target - nums[i]]即为答案

否则将当前元素及其下标添加到map中

代码

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        map<int,int> m;
        vector<int> result;
        for (int i = 0;i < nums.size();i++) 
        {
        	if (m.count(target - nums[i]))
        	{
        		result.push_back(i);
        		result.push_back(m[target - nums[i]]);
        		return result;
		}
        	m.insert(make_pair(nums[i],i));
	}
    }
};