hdu1081 To The Max

思路：先转换为一维的然后就随便做啦，注意可能相加起来小于0的情况

#include<bits\stdc++.h>
using namespace std;
int a[105][105];
#define INF 1e9
int main()
{
     int n;
	 while(scanf("%d",&n)!=EOF)
	 {
		 for(int i = 1;i<=n;i++)
			 for(int j = 1;j<=n;j++)
			 {
				 scanf("%d",&a[i][j]);
				 a[i][j]+=a[i][j-1];
			 }
		 int ans = -INF;
		 int res;
		 for(int i = 1;i<=n;i++)
			 for(int j = i;j<=n;j++)
				 for(int k = 1,res=0;k<=n;k++)
				 {
                      res+=a[k][j]-a[k][i-1];
					  if(res<0)
						  res=0;
					  ans = max(ans,res);
					  
				 }
		 printf("%d\n",ans);
	 }
}

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