hdu1506 Largest SubMatrix

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <string>
#include <stack>
#include <queue>

const int inf = (1<<31)-1;
const int MAXN = 1e3+10;
using namespace std;

char s[MAXN];
int a[MAXN][MAXN][3];
int L[MAXN][3];
int R[MAXN][3];

int main()
{
    int n,m;
    while(scanf("%d%d",&n,&m)==2){
        memset(a,0,sizeof(a));
        for(int i=1;i<=n;i++){
            scanf("%s",s);
            for(int j=0;j<m;j++){
                if(s[j]==‘a‘||s[j]==‘y‘||s[j]==‘w‘||s[j]==‘z‘)a[i][j+1][0] = a[i-1][j+1][0]+1;
                if(s[j]==‘b‘||s[j]==‘x‘||s[j]==‘w‘||s[j]==‘z‘)a[i][j+1][1] = a[i-1][j+1][1]+1;
                if(s[j]==‘c‘||s[j]==‘x‘||s[j]==‘y‘||s[j]==‘z‘)a[i][j+1][2] = a[i-1][j+1][2]+1;
            }
        }
        int ans,mmax = -inf;
        for(int i=1;i<=n;i++){

            a[i][0][0] = a[i][0][1] = a[i][0][2] = -1;
            a[i][m+1][0] = a[i][m+1][1] = a[i][m+1][2] = -1;

            for(int j=1;j<=m;j++){
                //L[j][0]=L[j][1] = L[j][2] = j;
                for(int k=0;k<3;k++){
                    L[j][k] = j;
                    while(a[i][j][k]<=a[i][L[j][k]-1][k])
                        L[j][k] = L[L[j][k]-1][k];
                }
            }
            for(int j=m;j>=1;j--){
                for(int k=0;k<3;k++){
                    R[j][k] = j;
                    while(a[i][j][k]<=a[i][R[j][k]+1][k])
                        R[j][k] = R[R[j][k]+1][k];
                }
            }
            for(int j=1;j<=m;j++){
                for(int k=0;k<3;k++){
                    ans = (R[j][k]-L[j][k]+1)*a[i][j][k];
                    mmax = max(ans,mmax);
                }
            }
        }
        cout<<mmax<<endl;
    }
    //cout << "Hello world!" << endl;
    return 0;
}