POJ3494Largest Submatrix of All 1’s（DP）

                                                                     Largest Submatrix of All 1’s

Time Limit: 5000MS		Memory Limit: 131072K
Total Submissions: 2740		Accepted: 971
Case Time Limit: 2000MS

Description

Given a m-by-n (0,1)-matrix, of all its submatrices of all 1’s which is the largest? By largest we mean that the submatrix has the most elements.

Input

The input contains multiple test cases. Each test case begins with m and n (1 ≤ m, n ≤ 2000) on line. Then come the elements of a (0,1)-matrix in row-major order on m lines each with n numbers. The input ends once EOF is met.

Output

For each test case, output one line containing the number of elements of the largest submatrix of all 1’s. If the given matrix is of all 0’s, output 0.

Sample Input

2 2
0 0
0 0
4 4
0 0 0 0
0 1 1 0
0 1 1 0
0 0 0 0

Sample Output

0
4

这个题目我不想多说，和2599一样。

#include
#include
#include
using namespace std;
int left1[2001],right1[2001],h[2001],n,m; 
char s[4020];
int main()
{
    while(scanf("%d%d",&n,&m)!=EOF)
    //while(cin>>n>>m)
    {
         int i,j,k,ans=0,temp;
         //memset(left,0,sizeof(left));
         //memset(right,0,sizeof(right));
         memset(h,0,sizeof(h));
         for(i=1;i<=m;i++)  
         {
              left1[i]=i;right1[i]=i;
         }
         getchar();
         for(i=1;i<=n;i++)
         {
               //for(j=1;j<=m;j++) 
               //{
                     //scanf("%d",&s);
               gets(s);
               for(j=1;j<=m;j++)
               {
                     if(s[2*j-2]=='1')  h[j]++;
                     else{  h[j]=0;}
                     left1[j]=j;right1[j]=j;
               } 
               //}
               for(j=2;j<=m;j++)
               {
                    if(h[j]==0)  continue;
                    for(k=j-1;k>0;) 
                    {
                        if(h[j]<=h[k])
                        {
                              left1[j]=left1[k];k=left1[k]-1;
                        }
                        else break;
                    }
               } 
               for(j=m-1;j>0;j--)
               {
                    if(h[j]==0)  continue;
                    for(k=j+1;k<=m;) 
                    {
                        if(h[j]<=h[k])
                        {
                              right1[j]=right1[k];k=right1[k]+1;
                        }
                        else break;         
                    }
               } 
               for(j=1;j<=m;j++)
               {
                    if(h[j]==0) continue;
                    temp=(right1[j]-left1[j]+1)*h[j];
                    if(temp>ans)  ans=temp;
               }
         } 
         cout<