Ural acm 1146. Maximum Sum

這是本人練ACM的第三個地方，剛剛一時想不起URAL帳號，上班幹活的沒心思了，然後去找回密碼，找到了，一會上班也有心思 了。哈哈

1146. Maximum Sum

Time limit: 1.0 second
Memory limit: 64 MB

Given a 2-dimensional array of positive and negative integers, find the sub-rectangle with the largest sum. 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. A sub-rectangle is any contiguous sub-array of size 1 × 1 or greater located within the whole array.

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-hand corner and has the sum of 15.

Input

The input consists of an N × N array of integers. The input begins with a single positive integer Non a line by itself indicating the size of the square two dimensional array. This is followed by N 2integers separated by white-space (newlines and spaces). These N 2 integers make up the array in row-major order (i.e., all numbers on the first row, left-to-right, then all numbers on 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

The output is the sum of the maximal sub-rectangle.

Sample

input	output
4 0 -2 -7 0 9 2 -6 2 -4 1 -4 1 -1 8 0 -2	15

code

#include <stdio.h>
int n,num[1010];
int number[1010][1010];
int main()
{
	int i,j,k,l,index,sum,maxsum;
	while(scanf("%d",&n)!=EOF)
	{
		
		for(i=0;i<n;i++)
			for(j=0;j<n;j++)
				scanf("%d",&number[i][j]);
		maxsum=number[0][0];
		for(i=0;i<n;i++)
		{
			for(j=i;j<n;j++)
			{
				sum=0;
				for(k=0;k<n;k++)
				{
					if(i==j)
						num[k]=number[j][k];
					else
						num[k]+=number[j][k];
					sum+=num[k];
				    if(sum>maxsum)
					    maxsum=sum;
					if(sum<0)
						sum=0;

				}
			}
		}
		printf("%d\n",maxsum);
	}
	return 0;
}