Bzoj 1800: [Ahoi2009]fly Flying Chess "Violence"

Description

Given a number of points on the circumference, the arc length between the point and the point is known, and the values are positive integers, arranged in a circular order. Please find out if there are any rectangles in these points and hope to find all the non-repeating rectangles in the shortest time.

Input

The first action is an integer n, which represents the number of points, and the next n rows are the individual arc lengths divided by the N points.

Output

The number of non-repeating rectangles that are formed

Sample Input

8
1
2
2
3
1
1
3
3

Sample Output

3

HINT

n<= 20

Idea: Well n<=20 tease me tut

#include <cstdio>

#include <string.h>

#include <iostream>

#include <algorithm>

#define MAXN 400009

#define LL Long Long

using namespace Std;

int SUM[MAXN],A[MAXN];

int main ()

{

int n,ans=0;

scanf ("%d", &n);

for (int i=1;i<=n;i++)

{

scanf ("%d", &a[i]);

Sum[i]+=sum[i-1]+a[i];

}

for (int i=1;i<=n;i++)

{

for (int j=i+1;j<=n;j++)

{

for (int k=j+1;k<=n;k++)

{

for (int l=k+1;l<=n;l++)

{

if (sum[l]-sum[j]== (sum[n]>>1) && Sum[l]-sum[k]==sum[j]-sum[i])

{

ans++;

}

}

}

}

}

printf ("%d\n", ans);

return 0;

}

Bzoj 1800: [Ahoi2009]fly Flight Chess "violence"