#include<bits/stdc++.h>
#define int long long
#define down(x) (1ll<<(2*(x)))
#define right(x) (1ll<<(2*(x)+1))
using namespace std;
const int SIZE = 3e5, MOD = 299987;

int f[2][SIZE][5], tot[2], d, st[2][SIZE], ans;

struct Hash {
	int nxt[SIZE], head[MOD + 50];
	inline void insert(int x, int s, int p) {
		int id = x % MOD + 1;
		for (int i = head[id]; i; i = nxt[i]) {
			if (st[d][i] == x) {
				f[d][i][p] += s;
				printf("f[%lld][%lld][%lld]=%lld   st=%lld\n", d, i, p, f[d][i][p], st[d][i]);
				return ;
			}
		}
		nxt[++tot[d]] = head[id];
		head[id] = tot[d];
		st[d][tot[d]] = x;
		f[d][tot[d]][p] = s;
		printf("f[%lld][%lld][%lld]=%lld   st=%lld\n", d, tot[d], p, f[d][tot[d]][p], st[d][tot[d]]);
	}
	inline void clear() {
		tot[d] = 0;
		memset(head, 0, sizeof head);
	}
} h;

char c[40];
int a[40][40], ex, ey;

signed main() {
	int n, m;
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		cin >> c + 1;
		for (int j = 1; j <= m; j++) {
			if (c[j] == '#')a[i][j] = 1;
			else {
				a[i][j] = 0;
				ex = i;
				ey = j;
			}
		}
	}
	h.insert(0, 1, 0);
	for (int i = 1; i <= n; i++) {
//		for(int j=1;j<=tot[d];j++)st[d][j]<<=2;
		for (int j = 1; j <= m; j++) {
			puts("------------------------------------------");
			printf("i=%d,j=%d\n", i, j);
			d ^= 1;
			h.clear();
			memset(f[d], 0, sizeof f[d]);
			for (int k = 1; k <= tot[d ^ 1]; k++) {
				int nst = st[d ^ 1][k], R = nst & right(j - 1), D = nst & down(j);
				for (int l = 0; l <= 3; l++) {
					int s = f[d ^ 1][k][l];
					printf("s=f[%lld][%lld][%lld]=%lld,st=%lld\n", d ^ 1, k, l, s, nst);
					int t = nst;
					if (t & right(j))t -= right(j);
					if (t & down(j))t -= down(j);
					if (a[i][j] == 1) {
						if (!D)h.insert(t, s, l);
					} else if (!R && !D) {
						h.insert(t, s, l);
						h.insert(t + down(j), s, l + 1);
						if (l == 3 && i == ex && j == ey) {
							ans += s;
							puts("!!!");
//						system("pause");
						}
					} else if (!R && D) {
						h.insert(t + down(j), s, l);
						h.insert(t + right(j), s, l);
					} else if (R && !D) {
						h.insert(t + right(j), s, l);
						h.insert(t + down(j), s, l);
						h.insert(t, s, l);
						/*if (l == 3 && i == ex && j == ey) {
							ans += s;
							puts("!!!");
//						system("pause");
						}*/
					}
				}
			}
		}
	}
	cout << ans;
	system("pause");
	return 0;
}

本题是在Windows下调试，这是带有调试信息的代码。

#include<bits/stdc++.h>
#define int long long
#define down(x) (1ll<<(2*(x)))
#define right(x) (1ll<<(2*(x)+1))
using namespace std;
const int SIZE = 3e5, MOD = 299987;

int f[2][SIZE][5], tot[2], d, st[2][SIZE], ans;

struct Hash {
	int nxt[SIZE], head[MOD + 50];
	inline void insert(int x, int s, int p) {
		int id = x % MOD + 1;
		for (int i = head[id]; i; i = nxt[i]) {
			if (st[d][i] == x) {
				f[d][i][p] += s;
				return ;
			}
		}
		nxt[++tot[d]] = head[id];
		head[id] = tot[d];
		st[d][tot[d]] = x;
		f[d][tot[d]][p] = s;
	}
	inline void clear() {
		tot[d] = 0;
		memset(head, 0, sizeof head);
	}
} h;

char c[40];
int a[40][40], ex, ey;

signed main() {
	int n, m;
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		cin >> c + 1;
		for (int j = 1; j <= m; j++) {
			if (c[j] == '#')a[i][j] = 1;
			else {
				a[i][j] = 0;
				ex = i;
				ey = j;
			}
		}
	}
	h.insert(0, 1, 0);
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			d ^= 1;
			h.clear();
			memset(f[d], 0, sizeof f[d]);
			for (int k = 1; k <= tot[d ^ 1]; k++) {
				int nst = st[d ^ 1][k], R = nst & right(j - 1), D = nst & down(j);
				for (int l = 0; l <= 3; l++) {
					int s = f[d ^ 1][k][l];
					int t = nst;
					if (t & right(j))t -= right(j);
					if (t & down(j))t -= down(j);
					if (a[i][j] == 1) {
						if (!D)h.insert(t, s, l);
					} else if (!R && !D) {
						h.insert(t, s, l);
						h.insert(t + down(j), s, l + 1);
						if (l == 3 && i == ex && j == ey) {
							ans += s;
						}
					} else if (!R && D) {
						h.insert(t + down(j), s, l);
						h.insert(t + right(j), s, l);
					} else if (R && !D) {
						h.insert(t + right(j), s, l);
						h.insert(t + down(j), s, l);
						h.insert(t, s, l);
						if (l == 3 && i == ex && j == ey) {
							ans += s;
						}
					}
				}
			}
		}
	}
	cout << ans;
	return 0;
}

这是删除调试信息的代码。 感激不尽。
样例没过，输出总是非常大。