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：

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        unordered_map<int, int> hashMap;
        int sz = nums.size();
        for(int i = 0; i < sz; i++)
            hashMap[nums[i]]++;
        
        unordered_map<int, int>::iterator itr = hashMap.begin();
        for(; itr != hashMap.end(); itr++)
        {
            if(itr->second == 1)
                return itr->first;
        }
        
        return INT_MIN;
    }
};