【POJ 3322】 Bloxorz I

【题目链接】

http://poj.org/problem?id=3322

【算法】

广度优先搜索

【代码】

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <limits>
#include <list>
#include <map>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <utility>
#include <vector>
#include <cwchar>
#include <cwctype>
#include <stack>
#include <limits.h>
using namespace std;
#define MAXN 510

int i,j,n,m;
char mp[MAXN][MAXN];

const int dx[] = {,,-,};
const int dy[] = {-,,,};
const int nx[][] = {{,,-,},{,,-,},{,,-,}};
const int ny[][] = {{-,,,},{-,,,},{-,,,}};
const int nxt[][] = {{,,,},{,,,},{,,,}};

struct info
{
        int x,y;
        int state;
};
inline bool ok(int x,int y)
{
        return x >=  && x <= n && y >=  && y <= m;
}
inline bool check(int x,int y,int state)
{
        if (!ok(x,y)) return false;
        if (state ==  && (mp[x][y] == '#' || mp[x][y] == 'E')) return false;
        if (state ==  && (!ok(x,y+) || mp[x][y] == '#' || mp[x][y+] == '#')) return false;
        if (state ==  && (!ok(x+,y) || mp[x][y] == '#' || mp[x+][y] == '#')) return false;
        return true;
}
inline void bfs()
{
        int i,j,k,tx,ty,ts;
        info s,e,cur;
        queue< info > q;
        static int dist[MAXN][MAXN][];
        while (!q.empty()) q.pop();
        for (i = ; i <= n; i++)
        {
                for (j = ; j <= m; j++)
                {
                        for (k = ; k < ; k++)
                        {
                                dist[i][j][k] = -;
                        }
                }
        }
        for (i = ; i <= n; i++)
        {
                for (j = ; j <= m; j++)
                {
                        if (mp[i][j] == 'X')
                        {
                                s.x = i;
                                s.y = j;
                                s.state = ;
                                for (k = ; k < ; k++)
                                {
                                        tx = i + dx[k];
                                        ty = j + dy[k];
                                        if (ok(tx,ty) && mp[tx][ty] == 'X')
                                        {
                                                s.x = min(i,tx);
                                                s.y = min(j,ty);
                                                if (k < ) s.state = ;
                                                else s.state = ;
                                        }
                                }
                        }
                        if (mp[i][j] == 'O')
                        {
                                e.x = i;
                                e.y = j;
                                e.state = ;
                        }
                }
        }
        dist[s.x][s.y][s.state] = ;
        q.push(s);
        while (!q.empty())
        {
                cur = q.front();
                q.pop();
                for (i = ; i < ; i++)
                {
                        tx = cur.x + nx[cur.state][i];
                        ty = cur.y + ny[cur.state][i];
                        ts = nxt[cur.state][i];
                        if (check(tx,ty,ts) && dist[tx][ty][ts] == -)
                        {
                                q.push((info){tx,ty,ts});
                                dist[tx][ty][ts] = dist[cur.x][cur.y][cur.state] + ;
                                if (tx == e.x && ty == e.y && ts == e.state)
                                {
                                        printf("%d\n",dist[tx][ty][ts]);
                                        return;
                                }
                        }
                }
        }
        printf("Impossible\n");
}

int main()
{

        while (scanf("%d%d",&n,&m) && n && m)
        {
                getchar();
                for (i = ; i <= n; i++)
                {
                        for (j = ; j <= m; j++)
                        {
                                mp[i][j] = getchar();
                        }
                        getchar();
                }
                bfs();
        }

        return ;

}