LeetCode1.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, 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

空间换时间，利用map标记出现过的数字和下标，一次遍历数组即可完成配对

代码

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