# 题目

## Description

Now here is a matrix with letter 'a','b','c','w','x','y','z' and you can change 'w' to 'a' or 'b', change 'x' to 'b' or 'c', change 'y' to 'a' or 'c', and change 'z' to 'a', 'b' or 'c'. After you changed it, what's the largest submatrix with the same letters you can make

## Input

The input contains multiple test cases. Each test case begins with m and n (1 ≤ m, n ≤ 1000) on line. Then come the elements of a matrix in row-major order on m lines each with n letters. 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 same letters.

2 4
abcw
wxyz

3

# 代码

```/*
By:OhYee
Github:OhYee
HomePage:http://www.oyohyee.com
Email:oyohyee@oyohyee.com

かしこいかわいい？
エリーチカ！

*/

#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <string>
#include <iostream>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <map>
#include <set>
using namespace std;

const int maxn = 1005;

char Mapa[maxn][maxn];
char Mapb[maxn][maxn];
char Mapc[maxn][maxn];

int H[maxn][maxn];
int Left[maxn][maxn];
int Right[maxn][maxn];
int MaxMatrix(char Matrix[maxn][maxn],int n,int m,char target) {
memset(H,0,sizeof(H));
memset(Left,0,sizeof(Left));
memset(Right,0,sizeof(Right));

for(int i = 1;i <= n;i++)
for(int j = 1;j <= m;j++) {
if(Matrix[i][j] == target) {
if(Matrix[i - 1][j])
H[i][j] = H[i - 1][j] + 1;
else
H[i][j] = 1;
}
}
for(int i = 1;i <= n;i++)
for(int j = 1;j <= m;j++) {
if(Matrix[i][j] == target) {
int t = j;
while(t >= 1 && H[i][j] <= H[i][t - 1])
t = Left[i][t - 1];
Left[i][j] = t;
}
}
for(int i = 1;i <= n;i++)
for(int j = m;j >= 1;j--) {
if(Matrix[i][j] == target) {
int t = j;
while(t <= m && H[i][j] <= H[i][t + 1])
t = Right[i][t + 1];
Right[i][j] = t;
}
}
int Max = 0;
for(int i = 1;i <= n;i++)
for(int j = 1;j <= m;j++) {
if(Matrix[i][j] == target) {
int S = H[i][j] * (Right[i][j] - Left[i][j] + 1);
Max = max(Max,S);
}
}
return Max;
}

bool  Do() {
int n,m;
if(scanf("%d%d",&n,&m) == EOF)
return false;
int a = 0,b = 0,c = 0;
for(int i = 1;i <= n;i++)
for(int j = 1;j <= m;j++) {
char t;
scanf("\n%c",&t);
Mapa[i][j] = (t == 'w' || t == 'y' || t == 'z') ? 'a' : t;
Mapb[i][j] = (t == 'w' || t == 'x' || t == 'z') ? 'b' : t;
Mapc[i][j] = (t == 'x' || t == 'y' || t == 'z') ? 'c' : t;
}

int ans = 0;
ans = max(ans,MaxMatrix(Mapa,n,m,'a'));
ans = max(ans,MaxMatrix(Mapb,n,m,'b'));
ans = max(ans,MaxMatrix(Mapc,n,m,'c'));

printf("%d\n",ans);
return true;
}

int main() {
while(Do());
return 0;
}

```