UVA--836 Largest Submatrix

Let A be an N×N matrix of zeros and ones. A submatrix S of A is any group
of contiguous entries that forms a square or a rectangle.
Write a program that determines the number of elements of the largest submatrix of ones in A. Largest here is measured by area.

Input

The input begins with a single positive integer on a line by itself indicating the number of the cases following, each of them as described below. This line is followed by a blank line, and there is also a blank line between two
consecutive inputs.

The matrix is given line by line. Each line consists of 0's and 1's. The order of the matrix is also the number of lines input and 1

N

25.

Output

For each test case, the output must follow the description below. The outputs of two consecutive cases will be separated by a blank line.

The output is the number of elements of the largest submatrix found.

Sample Input

1

10111000
00010100
00111000
00111010
00111111
01011110
01011110
00011110

Sample Output

16

憋了一天多的题 终于过了 代码如下 ：

<span style="font-size:14px;">#include<stdio.h>
#include<string.h>
int a[30][30];
int max1d(int a[],int l){
int sum,max_sum=-1e9;
int flog[30];
for(int i=0;i<l;i++){
memset(flog,0,sizeof(flog));
for(int j=i+1;j<l;j++){
if(a[j]!=a[i]||flog[j-1]==1)
flog[j]=1;
if(flog[j]==0)
sum=a[i]*(j-i+1);
else{
if(a[j]>a[i])
sum=a[j];
else sum=a[i];
}
if(sum>max_sum)
max_sum=sum;
}
}
return max_sum;
}
int main(){
int t,cnt=0;
scanf("%d",&t);
//getchar();
while(t--){
cnt++;
char str[30];
int s[30];
int flog[30];
int max_sum=-1e9;
getchar();
scanf("%s",str);
int l=strlen(str);
if(l==1){
if(cnt==1)
printf("%s\n",str);
else printf("\n%s\n",str);
}
else{
for(int i=0;i<l;i++)
a[0][i]=str[i]-'0';
for(int i=1;i<l;i++){
scanf("%s",str);
for(int j=0;j<l;j++)
a[i][j]=str[j]-'0';
}
for(int i=0;i<l;i++){
memset(s,0,sizeof(s));
memset(flog,0,sizeof(flog));
for(int k=0;k<l;k++){
s[k]=a[i][k];
flog[k]=a[i][k];
//printf("%d ",s[k]);
}
//printf("\n");
for(int j=i+1;j<l;j++){
for(int k=0;k<l;k++){
if(a[j][k]==1&&flog[k]==1)
s[k]+=a[j][k];
else flog[k]=0;
}
int sum=max1d(s,l);
/*for(int k=0;k<l;k++)
printf("%d ",s[k]);
printf("\n");*/
if(sum>max_sum)
max_sum=sum;
//printf("%d %d\n",sum,max_sum);
}
}
if(cnt==1)
printf("%d\n",max_sum);
else printf("\n%d\n",max_sum);
}
}
return 0;
}

</span>

看到一个更简单的实现 比我写的要简单很多 一针见血啊 我还需要学习 改进

<span style="font-size:14px;">#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int MAXN=30;
int n;
int max1(int* a){
//printf("8  ");for(int i=0;i<n;i++)printf("%d ",a[i]); puts("");
int ans=a[0],sum=a[0];
for(int i=1;i<n;i++){
if(a[i]==a[i-1]) sum+=a[i];
else sum=a[i];
ans=max(ans,sum);
}
//printf("15 ans=%d\n",ans);
return ans;
}
int max2(char a[][MAXN]){
//for(int i=0;i<n;i++) {for(int j=0;j<n;j++) printf("%c",a[i][j]);puts("");}
int ans=0,sum[MAXN];
for(int i=0;i<n;i++){
memset(sum,0,sizeof(sum));
for(int j=i;j<n;j++){
for(int k=0;k<n;k++){
if(a[j][k]=='1') sum[k]++;
else sum[k]=0;
}
//printf("30");for(int i=0;i<n;i++)printf(" %d",sum[i]); puts("");
ans=max(ans,max1(sum));
}
}
return ans;
}
int main(){
char a[MAXN][MAXN];
int i,t;
while(~scanf("%d",&t)){
while(t--){
scanf("%s",a[0]);
n=strlen(a[0]);
for(i=1;i<n;i++) scanf("%s",a[i]);
//for(i=0;i<n;i++) printf("%s\n",a[i]);
printf("%d\n",max2(a));
if(t) puts("");
}
}
}
</span>