poj3322 Bloxorz I

经典的方块游戏

1 * 2 * 1的砖块  最少步数到达一个指定的洞中

很明显的bfs，状态表示时用一个p值0，1， 2分别表示砖块立起来，横躺着和竖躺着，判重时用一个三维数组即可   vis  [p状态] [行位置] [列位置]

那么每次直接从一个状态转移到另一种状态，坐标位置同时改变即可

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
#include <string>
#include <cmath>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
//LOOP
#define FE(i, a, b) for(int i = (a); i <= (b); ++i)
#define REP(i, N) for(int i = 0; i < (N); ++i)
#define CLR(A,value) memset(A,value,sizeof(A))
//OTHER
#define PB push_back
//INPUT
#define RI(n) scanf("%d", &n)
#define RII(n, m) scanf("%d%d", &n, &m)
#define RS(s) scanf("%s", s)
typedef long long LL;
typedef unsigned long long ULL;
typedef vector <int> VI;
const double eps = 1e-9;
const int MOD = 1000000007;
const double PI = acos(-1.0);
const int INF = 0x3f3f3f3f;
const int maxn = 110;

int n, m;
char s[510][510];

int d[510][510][3];
bool vis[510][510][3];

int dir[][4][3] = {{{-2, 0, 2}, {0, 1, 1}, {1, 0, 2}, {0, -2, 1}},
                {{-1, 0, 0}, {0, 2, -1}, {1, 0, 0}, {0, -1, -1}},
                {{-1, 0, -2}, {0, 1, 0}, {2, 0, -2}, {0, -1, 0}}
                };

struct Node{
    int x, y;
    int p;
    Node(){}
    Node(int x, int y, int p): x(x), y(y), p(p){}
    bool operator == (const Node& a) const
    {
        return x == a.x && y == a.y && p == a.p;
    }
}st, ed, now, nxt;

inline void getorder(int &x1, int &y1, int &x2, int &y2, int &p)
{
    if (x1 > x2 || (x1 == x2 && y1 > y2))
    {
        swap(x1, x2);
        swap(y1, y2);
    }
    if (x1 == x2) p = 1;
    else p = 2;
    if (x1 == x2 && y1 == y2) p = 0;
}
vector<pair<int, int> > stv;

bool ok(int x, int y, int p)
{
    if (x < 0 || x >= n || y >= m || y < 0) return 0;
    if (p == 0)
    {
        if (s[x][y] == '#' || s[x][y] == 'E')   return 0;
        return 1;
    }
    if (s[x][y] == '#') return 0;
    int x2, y2;
    if (p == 1)
        x2 = x, y2 = y + 1;
    if (p == 2)
        x2 = x + 1, y2 = y;
    if (x2 < 0 || x2 >= n || y2 >= m || y2 < 0) return 0;
    if (s[x2][y2] == '#')   return 0;
    return 1;
}

int bfs()
{
    if (st == ed)   return 0;
    queue<Node>q;
    int x, y, p;
    CLR(vis, 0);
    d[st.x][st.y][st.p] = 0;
    vis[st.x][st.y][st.p] = 1;
    q.push(st);
    while (!q.empty())
    {
        now = q.front(); q.pop();
        REP(i, 4)
        {
            x = now.x + dir[now.p][i][0];
            y = now.y + dir[now.p][i][1];
            p = now.p + dir[now.p][i][2];
            if (!ok(x, y, p) || vis[x][y][p])
                continue;
            nxt.x = x, nxt.y = y, nxt.p = p;
            if (nxt == ed)  return d[now.x][now.y][now.p] + 1;
            d[x][y][p] = d[now.x][now.y][now.p] + 1;
            vis[x][y][p] = 1;
            q.push(nxt);
        }
    }
    return -1;
}

int main()
{
    //freopen("0.txt", "r", stdin);
    while (~RII(n, m) && n + m)
    {
        stv.clear();
        REP(i, n)
        {
            RS(s[i]);
            REP(j, m)
            {
                if (s[i][j] == 'X')
                {
                    s[i][j] = '.';
                    stv.push_back(make_pair(i, j));
                }
                if (s[i][j] == 'O')
                {
                    s[i][j] = '.';
                    ed.x = i; ed.y = j;
                    ed.p = 0;
                }
            }
        }
        int pp = 0;
        if (stv.size() == 2)
            getorder(stv[0].first, stv[0].second, stv[1].first, stv[1].second, pp);
        st.x = stv[0].first;
        st.y = stv[0].second;
        st.p = pp;
        int ans = bfs();
        if (ans == -1) puts("Impossible");
        else printf("%d\n", ans);
    }
    return 0;
}

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