LeetCode之“散列表”：Single Number

　　题目链接

　　题目要求：

　　Given an array of integers, every element appears twice except for one. Find that single one.

　　Note:
　　Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

　　这道题属于比较简单的，程序如下：

 1 class Solution {
 2 public:
 3     int singleNumber(vector<int>& nums) {
 4         unordered_map<int, int> hashMap;
 5         int sz = nums.size();
 6         for(int i = 0; i < sz; i++)
 7             hashMap[nums[i]]++;
 8
 9         unordered_map<int, int>::iterator itr = hashMap.begin();
10         for(; itr != hashMap.end(); itr++)
11         {
12             if(itr->second == 1)
13                 return itr->first;
14         }
15
16         return INT_MIN;
17     }
18 };