Codeforces Round #290 (Div. 2) B. Fox And Two Dots（DFS）

http://codeforces.com/problemset/problem/510/B

#include "cstdio"
#include "cstring"
int r,c;
char map[][];
int vis[][];
int mark;
int dx[]={,-,,},dy[]={,,,-};
int judge(int x,int y)
{
    if(x<||x>=r||y<||y>=c)
        return ;
    return ;
}
void dfs(int x,int y,int perX,int perY)
{
    if(!judge(x,y))
        return;
    vis[x][y]=;
    for(int i=;i<;i++)
    {
        int xx=x+dx[i];
        int yy=y+dy[i];
        if(map[xx][yy]==map[x][y]&&judge(xx,yy)&&(xx!=perX||yy!=perY))
        {
            if(vis[xx][yy])
            {
                mark=;
                return;
            }
            dfs(xx,yy,x,y);
        }
    }
    return;
}
int main()
{
    while(scanf("%d%d",&r,&c)!=EOF)
    {
        memset(vis,,sizeof(vis));
        for(int i=;i<r;i++)
            scanf("%s",map[i]);
        mark=;
        int flag=;
        for(int i=;i<r;i++)
        {
            for(int j=;j<c;j++)
            {
                if(!vis[i][j])
                {
                    dfs(i,j,,);
                   if(mark)
                    {
                        break;
                    }
                }
            }
           if(mark)
            {
                break;
            }
        }
        if(mark)
            printf("Yes\n");
        else
            printf("No\n");

    }
    return ;
}