codeforces_B. Forgery

http://codeforces.com/contest/1059/problem/B

题意：

For simplicity, the signature is represented as an n×mn×m grid, where every cell is either filled with ink or empty. Andrey's pen can fill a 3×33×3square without its central cell if it is completely contained inside the grid, as shown below.

xxx
x.x
xxx

Determine whether is it possible to forge the signature on an empty n×mn×m grid.

思路：

模拟。在给定的签名中寻找特定的点，该点的所有相邻点均被涂色，找到该点，将另一张空白纸上的该点相邻的点涂色，最后比较两张图是否相同。

#include<cstdio>
#include<iostream>
#include<algorithm>
using namespace std;
#define LL long long

char a[][],b[][];

bool legal(int x,int y)
{
    for(int i=-; i<=; i++)
        for(int j=-; j<=; j++)
        {
            if(i==&&j==)
                continue;
            if(a[x+i][y+j]=='.')
                return ;
        }
    return ;
}

void draw(int x,int y)
{
    for(int i=-; i<=; i++)
        for(int j=-; j<=; j++)
        {
            if(i==&&j==)
                continue;
            b[x+i][y+j]='#';
        }
}

int n,m;
bool compareAB()
{
    for(int i=; i<n; i++)
        for(int j=; j<m; j++)
            if(a[i][j]!=b[i][j])
                return ;
    return ;
}

int main()
{

    while(scanf("%d%d",&n,&m)!=EOF)
    {
        for(int i=;i<n;i++)
            for(int j=;j<m;j++)
                b[i][j]='.';
        for(int i=; i<n; i++)
            scanf("%s",a[i]);
        for(int i=; i<n-; i++)
            for(int j=; j<m-; j++)
            {
                if(legal(i,j))
                    draw(i,j);
            }
        if(compareAB())
            printf("YES\n");
        else
            printf("NO\n");
    }
    return ;
}