【HDOJ】1732 Push Box

BFS.使用当前结点位置以及三个箱子的位置作为状态。

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

#define MAXN 8

typedef struct {
    int x, y;
} Point_t;

typedef struct {
    Point_t v;
    Point_t box[3];
    int t;
} Node_t;

Node_t cur;
bool visit[MAXN][MAXN][MAXN][MAXN][MAXN][MAXN][MAXN][MAXN];
char map[MAXN+5][MAXN+5];
int dir[4][2] = {
    {-1,0}, {1,0}, {0,-1}, {0,1}
};
int n, m;

bool check(int x, int y) {
    return x<0 || x>=n || y<0 || y>=m || map[x][y]=='#';
}

bool getVisit(Node_t a) {
    return     visit[a.v.x][a.v.y][a.box[0].x][a.box[0].y][a.box[1].x][a.box[1].y][a.box[2].x][a.box[2].y];
}

void setVisit(Node_t a) {
    visit[a.v.x][a.v.y][a.box[0].x][a.box[0].y][a.box[1].x][a.box[1].y][a.box[2].x][a.box[2].y] = true;
}

bool isFinish(Node_t a) {
    return map[a.box[0].x][a.box[0].y]=='@' && map[a.box[1].x][a.box[1].y]=='@' &&
            map[a.box[2].x][a.box[2].y]=='@';
}

bool boxCanMove(Node_t a, int d, int id) {
    int x = a.v.x + dir[d][0];
    int y = a.v.y + dir[d][1];

    if (check(x, y))
        return false;

    for (int i=0; i<3; ++i) {
        if (i!=id && a.box[i].x==x && a.box[i].y==y)
            return false;
    }

    return true;
}

void printNode(Node_t a) {
    printf("a.v.x = %d, a.v.y = %d
", a.v.x, a.v.y);
    for (int i=0; i<3; ++i) {
        printf("a.box[%d].x = %d, a.box[%d].y = %d
", i, a.box[0].x, i, a.box[0].y);
    }
}

int bfs() {
    queue<Node_t> Q;
    int i, j, k;
    int x, y;

    memset(visit, false, sizeof(visit));
    cur.t = 0;
    setVisit(cur);
    Q.push(cur);

    while (!Q.empty()) {
        Node_t d = Q.front();
        Q.pop();
#ifndef ONLINE_JUDGE
        printNode(d);
#endif
        if (isFinish(d)) {
            return d.t;
        }

        for (i=0; i<4; ++i) {
            x = d.v.x + dir[i][0];
            y = d.v.y + dir[i][1];
            if (check(x, y))
                continue;
            Node_t nd = d;
            nd.v.x = x;
            nd.v.y = y;
            ++nd.t;
            for (j=0; j<3; ++j) {
                if (nd.box[j].x == x && nd.box[j].y == y) {
                    break;
                }
            }
            if (j<3) {
                /* next is a box*/
                if (boxCanMove(nd, i, j)) {
                    nd.box[j].x += dir[i][0];
                    nd.box[j].y += dir[i][1];
                } else {
                    continue;
                }
            }

            if (!getVisit(nd)) {
                setVisit(nd);
                Q.push(nd);
            }
        }
    }

    return -1;
}

int main() {
    int i, j, k;

    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
    #endif

    while (scanf("%d %d", &n, &m) != EOF) {
        k = 0;
        for (i=0; i<n; ++i) {
            scanf("%s", map[i]);
            for (j=0; j<m; ++j) {
                if (map[i][j] == 'X') {
                    cur.v.x = i;
                    cur.v.y = j;
                } else if (map[i][j] == '*') {
                    cur.box[k].x = i;
                    cur.box[k].y = j;
                    ++k;
                }
            }
        }

        k = bfs();
        printf("%d
", k);
    }

    return 0;
}