usaco 2.1 castle...

在移除房间北墙的时候忘了移除该房间北邻的南墙，wa了一次，注意移墙时的搜索顺序：自底向上，自左向右。

/*
    ID:chenjiong
    PROG:castle
    LANG:C++
*/

#include <stdio.h>
#include <string.h>

const int MAXN = 55;

typedef struct {
    int dir[4][3];     //西北东南
}POS;

typedef struct {
    int x;
    int y;
    char d;
    int size;
}WALL;

int M,N;
POS map[MAXN][MAXN];
bool vis[MAXN][MAXN];
int area;        //the size of a certain room
int cnt;         //the number of rooms
WALL result;

bool is_in(int x,int y)
{
    if ( x >= 1 && x <= N && y >= 1 && y <= M )
        return true;
    return false;
}

void init(POS& x,int wall)
{
    switch ( wall )
    {
        case 0 : break;
    
        case 1 : x.dir[0][2] = 0; break;
        case 2 : x.dir[1][2] = 0; break;
        case 4 : x.dir[2][2] = 0; break;
        case 8 : x.dir[3][2] = 0; break;
        
        case 3 : x.dir[0][2] = x.dir[1][2] = 0; break;
        case 5 : x.dir[0][2] = x.dir[2][2] = 0; break;
        case 9 : x.dir[0][2] = x.dir[3][2] = 0; break;
        case 6 : x.dir[1][2] = x.dir[2][2] = 0; break;
        case 10 : x.dir[1][2] = x.dir[3][2] = 0; break;
        case 12 : x.dir[2][2] = x.dir[3][2] = 0; break;
        
        case 7 : x.dir[0][2] = x.dir[1][2] = x.dir[2][2] = 0; break;
        case 11 : x.dir[0][2] = x.dir[1][2] = x.dir[3][2] = 0; break;
        case 13 : x.dir[0][2] = x.dir[2][2] = x.dir[3][2] = 0; break;
        case 14 : x.dir[1][2] = x.dir[2][2] = x.dir[3][2] = 0; break;
        
        case 15 : x.dir[0][2] = x.dir[1][2] = x.dir[2][2] = x.dir[3][2] = 0; break;
    }
}

void dfs(int x,int y)
{
    vis[x][y] = true;
    area++;

    int xx,yy;
    int i;
    for ( i = 0; i < 4; i++)
    {
        if ( map[x][y].dir[i][2] == 1 )
        {
            xx = x + map[x][y].dir[i][0];
            yy = y + map[x][y].dir[i][1];
            if ( is_in(xx,yy) && !vis[xx][yy] )
                dfs(xx,yy);
        }
    }
}

int floodfill()
{
    memset(vis,0,sizeof(vis));
    int max = 0;
    int i,j;
    for ( i = 1; i <= N; i++)
    {
        for ( j = 1; j <= M; j++)
        {
            if ( !vis[i][j] )
            {
                area = 0;
                cnt++;
                dfs(i,j);
                if ( area > max )
                    max = area;
            }
        }
    }
    return max;
}

void remove(int x,int y,const char d)
{
    if ( d == 'N' )
    {
        if ( map[x][y].dir[1][2] == 1 )
            return;
        else
        {
            map[x][y].dir[1][2] = 1;
            map[x - 1][y].dir[3][2] = 1;
            int tmp = floodfill();
            if ( tmp > result.size )
            {
                result.x = x;
                result.y = y;
                result.d = 'N';
                result.size = tmp;
            }
            map[x][y].dir[1][2] = 0;
            map[x - 1][y].dir[3][2] = 0;
        }
    }
    else
    {
        if ( map[x][y].dir[2][2] == 1 )
            return;
        else
        {
            map[x][y].dir[2][2] = 1;
            map[x][y + 1].dir[0][2] = 1;
            int tmp = floodfill();
            if ( tmp > result.size )
            {
                result.x = x;
                result.y = y;
                result.d = 'E';
                result.size = tmp;
            }
            map[x][y].dir[2][2] = 0;
            map[x][y + 1].dir[0][2] = 0;
        }
    }
}

int main()
{
    freopen("castle.in","r",stdin);
    freopen("castle.out","w",stdout);

    int i,j;
    for ( i = 0; i < MAXN; i++)
    {
        for ( j = 0; j < MAXN; j++)
        {
            map[i][j].dir[0][0] = 0; 
            map[i][j].dir[0][1] = -1;
            map[i][j].dir[0][2] = 1;

            map[i][j].dir[1][0] = -1;
            map[i][j].dir[1][1] = 0;
            map[i][j].dir[1][2] = 1;

            map[i][j].dir[2][0] = 0;
            map[i][j].dir[2][1] = 1;
            map[i][j].dir[2][2] = 1;

            map[i][j].dir[3][0] = 1;
            map[i][j].dir[3][1] = 0;
            map[i][j].dir[3][2] = 1;
        }
    }

    scanf("%d%d",&M,&N);
    int tmp;
    for ( i = 1; i <= N; i++)
    {
        for ( j = 1; j <= M; j++)
        {
            scanf("%d",&tmp);
            init(map[i][j],tmp);
        }
    }

    int ans = floodfill();
    printf("%d\n%d\n",cnt,ans);
    
    for ( j = 1; j <= M; j++)
    {
        for ( i = N; i >= 1; i--)
        {
            remove(i,j,'N');
            remove(i,j,'E');
        }
    }
    
    printf("%d\n%d %d %c\n",result.size,result.x,result.y,result.d);

    return 0;
}