【LeetCode136】Single Number

#include <iostream>
#include <vector>
#include <unordered_map>
using namespace std;

class Solution {
public:
    int singleNumber(vector <int>& nums) {
        unordered_map<int, int> ump;
        for(int i = 0; i < nums.size(); ++i){
            unordered_map<int, int>::iterator p = ump.find(nums[i]);
            if(p != ump.end())
                ump.erase(p);
            else
                ump.insert(make_pair(nums[i], i));
        }
        return ump.begin()->first;
    }
};


int main(int argc, char *argv[])
{
    int test[] = {1, 2, 9, 2, 1};
    vector <int> test1(test, test+5);
    Solution sol;
    cout << sol.singleNumber(test1) << endl;
    return 0;
}