AStar

1 POJ 1475 Pushing Boxes

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <queue>
#include <vector>
#include <stack>
#include <map>
#include <set>
#include <cmath>
#include <cctype>
#include <ctime>

using namespace std;

#define REP(i, n) for (int i = 0; i < (n); ++i)
#define eps 1e-9
#define SZ(x) ((int)x.size())
#define x first
#define y second
#define y1 Y1

typedef unsigned long long ll;
typedef pair<int, int> pii;
struct Node {
    pii s, b; int push, walk;
    bool operator < (const Node& rhs) const {
        return push > rhs.push || (push == rhs.push && walk > rhs.walk);
    }
};
const int maxn = 30;
int n, m, Case = 0;
char G[maxn][maxn], path[maxn * maxn];
pii S, B, T;
bool flag;
int dir[][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
int fa[maxn][maxn][maxn][maxn][5], h[maxn][maxn][maxn][maxn][2];

bool check(int x, int y) {
    return (1 <= x && x <= n && 1 <= y && y <= m && G[x][y] != '#');
}
void print(int x, int y, int len) {
    int x1 = T.x, y1 = T.y, fx, fy, fx1, fy1, len_t = len; char c;
    while (len--) {
        fx = fa[x][y][x1][y1][0]; fy = fa[x][y][x1][y1][1];
        fx1 = fa[x][y][x1][y1][2]; fy1 = fa[x][y][x1][y1][3];
        c = 'a'; if (fx1 != x1 || fy1 != y1) { c = 'A'; }
        if (x - fx == -1) { path[len] = 'N' - 'A' + c; }
        else if (x - fx == 1) { path[len] = 'S' - 'A' + c; }
        else if (y - fy == -1) { path[len] = 'W' - 'A' + c; }
        else { path[len] = 'E' - 'A' + c; }
        x = fx; y = fy; x1 = fx1; y1 = fy1;
    }
    for (int i = 0; i < len_t; ++i) { printf("%c", path[i]); }
}
bool is_best(int x1, int y1, int x2, int y2, int push, int walk) {
    if (push != h[x1][y1][x2][y2][0]) { return push < h[x1][y1][x2][y2][0]; }
    return walk < h[x1][y1][x2][y2][1];
}
void set_best(int x1, int y1, int x2, int y2, int push, int walk) {
    h[x1][y1][x2][y2][0] = push; h[x1][y1][x2][y2][1] = walk;
}
void AStar() {
    memset(fa, 0, sizeof(fa)); memset(h, 0x3f3f3f3f, sizeof(h));
    priority_queue<Node> q; Node t1, t2;
    t1.s = S; t1.b = B; t1.push = t1.walk = 0; q.push(t1);
    while (!q.empty()) {
        t1 = q.top(); q.pop();
        if (t1.b == T) { print(t1.s.x, t1.s.y, t1.push + t1.walk); flag = true; break; }
        for (int i = 0; i < 4; ++i) {
            t2 = t1; t2.s.x += dir[i][0]; t2.s.y += dir[i][1];
            if (!check(t2.s.x, t2.s.y)) { continue; }
            if (t2.s == t2.b) {
                t2.b.x += dir[i][0]; t2.b.y += dir[i][1];
                if (!check(t2.b.x, t2.b.y)) { continue; } ++t2.push;
            } else { ++t2.walk; }
            if (!is_best(t2.s.x, t2.s.y, t2.b.x, t2.b.y, t2.push, t2.walk)) { continue; }
            fa[t2.s.x][t2.s.y][t2.b.x][t2.b.y][0] = t1.s.x;
            fa[t2.s.x][t2.s.y][t2.b.x][t2.b.y][1] = t1.s.y;
            fa[t2.s.x][t2.s.y][t2.b.x][t2.b.y][2] = t1.b.x;
            fa[t2.s.x][t2.s.y][t2.b.x][t2.b.y][3] = t1.b.y;
            set_best(t2.s.x, t2.s.y, t2.b.x, t2.b.y, t2.push, t2.walk); q.push(t2);
        }
    }
}

int main() {
#ifdef __AiR_H
    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);
#endif // __AiR_H
    while (scanf("%d %d", &n, &m) != EOF) {
        if (n == 0 && m == 0) { break; }
        for (int i = 1; i <= n; ++i) {
            scanf("%s", G[i] + 1);
            for (int j = 1; j <= m; ++j) {
                if (G[i][j] == 'S') { S.x = i; S.y = j; }
                else if (G[i][j] == 'B') { B.x = i; B.y = j; }
                else if (G[i][j] == 'T') { T.x = i; T.y = j; }
            }
        }
        printf("Maze #%d
", ++Case); flag = false; AStar();
        if (!flag) { printf("Impossible."); } printf("

");
    }
#ifdef __AiR_H
    printf("Time used = %.2fs
", (double)clock() / CLOCKS_PER_SEC);
#endif // __AiR_H
    return 0;
}