LeetCode Problem 1.Two Sum

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].

代码如下：

 1 class Solution {
 2 public:
 3     vector<int> twoSum(vector<int>& nums, int target)
 4     {
 5         unordered_map<int, int> hashmap;
 6         vector<int> result;
 7
 8         for (int i = 0; i < nums.size(); ++i)
 9         {
10             if (hashmap.find(target - nums[i]) != hashmap.end())
11             {
12                 result.push_back(hashmap[target - nums[i]]);
13                 result.push_back(i);
14                 return result;
15             }
16             else
17             {
18                 hashmap[nums[i]] = i;
19             }
20         }
21         return result;
22     }
23 };