学步园

#include <stdio.h>  
#include <string.h>  

int main()  
{  
	const int size = 101;  
	int Max,sum;  
	int N,i,j,k,val,a[size][size];  
	while (scanf("%d",&N)!=EOF)  
	{  
		memset(a,0,sizeof(a));  
		Max = -128;  
		for(i=1;i<=N;i++)  
			for(j=1;j<=N;j++)  
			{  
				scanf("%d",&val);  
				a[i][j]+=a[i][j-1]+val;//a[i][j]表示第i行前j个数之和  
			}  
			for(i=1;i<=N;i++)  //起始列
				for (j=i;j<=N;j++)  //终止列
					for(sum = 0,k=1;k<=N;k++) //对每一行进行搜索
					{  
						//a[k][j]-a[k][i-1]表示第k行第j列与第i列之间的数  
						sum=(sum>0?sum:0)+a[k][j]-a[k][i-1];  
						if(sum>Max)  
							Max = sum;  
					}  
					printf("%d\n",Max);  
	}  
}