hdu 1885 bfs+状压

和上一个题基本一样。

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cctype>
#include <queue>
#include <map>
using namespace std;

const int N = 101;
char maze[N][N];
bool visit[N][N][1 << 4];
int dx[] = { 0, 0, 1, -1 };
int dy[] = { 1, -1, 0, 0 };
int n, m, sx, sy;
map<char, int> mp;

void init()
{
    mp['B'] = 0;    mp['b'] = 0;
    mp['Y'] = 1;    mp['y'] = 1;
    mp['R'] = 2;    mp['r'] = 2;
    mp['G'] = 3;    mp['g'] = 3;
}

bool ok( int x, int y )
{
    return x >= 0 && x < n && y >= 0 && y < m;
}

struct Node 
{
    int x, y, step, state;
    Node(){}
    Node( int _x, int _y, int _step, int _state )
    {
        x = _x, y = _y, step = _step, state = _state;
    }
};

bool uc( char ch )
{
    return ch == 'B' || ch == 'Y' || ch == 'R' || ch == 'G';
}

bool lc( char ch )
{
    return ch == 'b' || ch == 'y' || ch == 'r' || ch == 'g';
}

queue<Node> q;

int bfs()
{
    while ( !q.empty() ) q.pop();
    memset( visit, false, sizeof(visit) );
    q.push( Node( sx, sy, 0, 0 ) );
    visit[sx][sy][0] = true;
    while ( !q.empty() )
    {
        Node cur = q.front();
        q.pop();
        if ( maze[cur.x][cur.y] == 'X' ) return cur.step;
        for ( int i = 0; i < 4; i++ )
        {
            int xx = cur.x + dx[i];
            int yy = cur.y + dy[i];
            if ( ok( xx, yy ) )
            {
                if ( maze[xx][yy] == '#' ) continue;
                if ( uc( maze[xx][yy] ) )
                {
                    int tmp = ( 1 << mp[maze[xx][yy]] );
                    if ( ( cur.state & tmp ) && !visit[xx][yy][cur.state] )
                    {
                        q.push( Node( xx, yy, cur.step + 1, cur.state) );
                        visit[xx][yy][cur.state] = true;
                    }
                }
                else if ( lc( maze[xx][yy] ) )
                {
                    int tmp = ( 1 << mp[maze[xx][yy]] );
                    if ( !visit[xx][yy][cur.state | tmp] )
                    {
                        q.push( Node( xx, yy, cur.step + 1, cur.state | tmp ) );
                        visit[xx][yy][cur.state | tmp] = true;
                    }
                }
                else
                {
                    if ( !visit[xx][yy][cur.state] )
                    {
                        q.push( Node( xx, yy, cur.step + 1, cur.state ) );
                        visit[xx][yy][cur.state] = true;
                    }
                }
            }
        }
    }
    return -1;
}

int main ()
{
    init();
    while ( scanf("%d%d", &n, &m) != EOF )
    {
        if ( !n && !m ) break;
        int x = 0;
        for ( int i = 0; i < n; i++ )
        {
            scanf("%s", maze[i]);
            for ( int j = 0; j < m; j++ )
            {
                if ( maze[i][j] == '*' )
                {
                    sx = i;
                    sy = j;
                    maze[i][j] = '.';
                }
                else if ( maze[i][j] == 'X' )
                {
                    x++;
                }
            }
        }
        if ( x == 0 || ( x = bfs() ) == -1 )
        {
            printf("The poor student is trapped!
");
        }
        else
        {
            printf("Escape possible in %d steps.
", x);
        }
    }
    return 0;    
}