leetcode-1-two sum

一个很好的leetcode题解博客：点击打开链接

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].

思路：遍历每个数得到target-数之后的结果看有没有对应，如果有的话返回其索引。所以想到建立数与下标之间的索引。空间换时间。

class Solution {
public:
    vector twoSum(vector& nums, int target) {
        unordered_map m; //建立索引表
        for(int i=0;i ret(2);
        for(int i=0;i