腾讯模拟笔试

#include <bits/stdc++.h>
using namespace std;

int main(){
    int n;
    std::ios::sync_with_stdio(false);
    map<long long, int> temp;
    while (cin >> n)
    {
        int n2 = n;
        while (n--)
        {
            long long a;
            cin >> a;
            if (temp[a] == 0)
            {
                temp[a]=1;
            }
            else temp[a] = 0;
        }
        long long sum = 0;
        bool flag;
        if (n2 & 1)
        {
            flag = 1;
            for (auto i : temp)
            {
                if (i.second == 1)
                {
                    if (flag)
                        sum += i.first;
                    else
                        sum -= i.first;
                    flag = !flag;
                }
            }
        }
        else
        {
            flag = 1;
            for (auto i : temp)
            {
                if (i.second == 1)
                {
                    if (flag)
                        sum -= i.first;
                    else
                        sum += i.first;
                    flag = !flag;
                }
            }
        }
        cout << sum << endl;
    }
    return 0;
}