To the max(hdu1081)

#include<iostream>
#include<stdlib.h>
#include<math.h>
#include<stdio.h>
#include<algorithm>
#include<queue>
#include<string.h>
#include<stack>
#include<math.h>

using namespace std;


int main()
{
    int i,j,k;
    int go[100][100];
    int n;
    int a[100],b[100];
    int maxnum;
    int f;
    int ans=0;

    while (cin>>n)
    {
    for (i=0;i<n;i++)
        for (j=0;j<n;j++)
            cin>>go[i][j];
    maxnum=-10000000;
    for (k=0;k<n;k++)
    {
        memset(a,0,sizeof(a));
        for (j=k;j<n;j++)
        {
            for (i=0;i<n;i++)
                a[i]+=go[j][i];
            f=0;
            for (i=0;i<n;i++)
            {
                if (f+a[i]>=0)
                    f+=a[i];
                else
                    f=0;
                if (f>maxnum)
                    maxnum=f;
            }
        }
    }
    cout<<maxnum<<endl;
    }}

Problem Description

Given a two-dimensional array of positive and negative integers, a sub-rectangle is any contiguous sub-array of size 1 x 1 or greater located within the whole array. The sum of a rectangle is the sum of all the elements in that rectangle. In this problem the sub-rectangle with the largest sum is referred to as the maximal sub-rectangle.

As an example, the maximal sub-rectangle of the array:

0 -2 -7 0
9 2 -6 2
-4 1 -4 1
-1 8 0 -2

is in the lower left corner:

9 2
-4 1
-1 8

and has a sum of 15.

 

Input

The input consists of an N x N array of integers. The input begins with a single positive integer N on a line by itself, indicating the size of the square two-dimensional array. This is followed by N 2 integers separated by whitespace (spaces and newlines). These are the N 2 integers of the array, presented in row-major order. That is, all numbers in the first row, left to right, then all numbers in the second row, left to right, etc. N may be as large as 100. The numbers in the array will be in the range [-127,127].

 

Output

Output the sum of the maximal sub-rectangle.

 

Sample Input

4 0 -2 -7 0 9 2 -6 2 -4 1 -4 1 -1 8 0 -2

 

Sample Output

15