『AGC 012A』AtCoder Group Contest

Problem

Time limit : 2sec / Memory limit : 256MB

题意：给$3N$个数，$3​$个一组，我们取每个组第二大的数出来相加，问最大能够是多少

还是…还是弄个door吧。。

door♂

Solution

排序，取$2,4,6,8\dots$就行

Code:

#include<bits/stdc++.h>
using namespace std;
#define ll long long
ll sum = 0;
ll a[3 * 123456];
bool cmd(ll x, ll y)
{
	return x > y;
}
int n;
inline void _read(int &x)
{
	x = 0;
	char t = getchar();
	while (!isdigit(t)) t = getchar();
	while (isdigit(t))
	{
		x = x * 10 + t - '0';
		t = getchar();
	}
}
inline void _read(ll &x)
{
	x = 0;
	char t = getchar();
	while (!isdigit(t)) t = getchar();
	while (isdigit(t))
	{
		x = x * 10 + t - '0';
		t = getchar();
	}
}
int main()
{
	_read(n);
	for (int i = 1; i <= 3 * n; i++) _read(a[i]);
	int i = 2;
	sort(a + 1, a + 1 + 3 * n, cmd);
	while (n--)
	{
		sum += a[i];
		i += 2;
	}
	printf("%lld", sum);
	return 0;
}