1. Two Sum

找到數組中和為target的兩個數，返回索引

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].

 1 class Solution {
 2 public:
 3     vector<int> twoSum(vector<int>& nums, int target) {
 4         unordered_map<int, int> hash;
 5         vector<int> result;
 6         for (int i = 0; i < nums.size(); i++) {
 
 7             if (hash.find(target - nums[i]) != hash.end()) {
 8                 result.push_back(hash[target - nums[i]]);
 9                 result.push_back(i);
10                 return result;
11             }
12             hash[nums[i]] = i;
13         }
14         return result;
15     }
16 };

leetcode筆記—Array