【算法题】

#include<stdio.h>#include<vector>#include <algorithm>#include <iostream>#include <functional>using namespace std;const unsigned int MAX = 100005;unsigned int n;vector<int> vec;int main(){    long long sum(0);//避免累加时溢出    scanf("%d", &n);    n *= 3;    vec.resize(n);    register int i;    for (i = 0; i < n;++i)    {        scanf("%d", &vec[i]);    }    sort(vec.begin(), vec.end(),greater<int>());    int tmp = 1;    n = n / 3;    for (int x = 0; x < n; ++x)    {        sum += vec[tmp];        tmp += 2;    }    cout << sum;    return 0;}