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 };
原文：http://www.cnblogs.com/fqwCpp/p/5613201.html