UVa 10047 - The Monocycle (多状态BFS)

题目链接：https://onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&category=0&problem=988&mosmsg=Submission+received+with+ID+26578514

\(d[x][y][dir][c\) 记录位置，朝向，颜色，\(BFS\) 求解即可

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;

const int maxn = 55;
const int INF = 0x3f3f3f3f;

int n, m; 
char ch[maxn];

int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, 1, 0, -1};

int sx, sy, tx, ty;

int a[maxn][maxn];
int d[maxn][maxn][10][10];
int vis[maxn][maxn][10][10];
int tc[10] = {1, 2, 3, 4, 0};
int td[2][10] = {{1, 2, 3, 0}, {3, 0, 1, 2}}; // 0 N 1 E 2 S 3 W

struct Node{
	int x, y, d, c;
	Node(int x, int y, int d, int c): x(x), y(y), d(d), c(c) {};
};

int bfs(){
	memset(vis, 0, sizeof(vis));
	memset(d, 0x3f, sizeof(d));
	queue<Node> q;
	d[sx][sy][0][0] = 0;
	q.push(Node(sx, sy, 0, 0));
	
	while(!q.empty()){
		Node p = q.front(); q.pop();
		
		if(vis[p.x][p.y][p.d][p.c]) continue;
		vis[p.x][p.y][p.d][p.c] = 1;
				
		if(p.x == tx && p.y == ty && p.c == 0){
			return d[p.x][p.y][p.d][p.c]; 
		}
		
//		int x = p.x + dx[p.d], y = p.y + dy[p.d], c = tc[p.c]; // 移动 
		int x = p.x + dx[p.d], y = p.y + dy[p.d], c = tc[p.c];
		if(x >= 1 && x <= n && y >= 1 && y <= m && !a[x][y] && !vis[x][y][p.d][c]){
			d[x][y][p.d][c] = d[p.x][p.y][p.d][p.c] + 1;
			q.push(Node(x, y, p.d, c));
		}
		
		for(int i = 0 ; i < 2 ; ++i){ // 转向 
			int dir = td[i][p.d];
			if(!vis[p.x][p.y][dir][p.c]){
				d[p.x][p.y][dir][p.c] = d[p.x][p.y][p.d][p.c] + 1;
				q.push(Node(p.x, p.y, dir, p.c));
			}
		}
	}
	
	return INF;
}

ll read(){ ll s = 0, f = 1; char ch = getchar(); while(ch < '0' || ch > '9'){ if(ch == '-') f = -1; ch = getchar(); } while(ch >= '0' && ch <= '9'){ s = s * 10 + ch - '0'; ch = getchar(); } return s * f; }

int main(){
	int flag = 0;
	int kase = 0;
	while(scanf("%d%d", &n, &m) && (n || m)){
		if(flag) printf("\n");
		flag = 1; 
		for(int i = 1 ; i <= n ; ++i){
			scanf("%s", ch + 1);
			for(int j = 1 ; j <= m ; ++j){
				if(ch[j] == '#') a[i][j] = 1;
				else if(ch[j] == '.'){
					a[i][j] = 0;
				} else if(ch[j] == 'S'){
					sx = i, sy = j;
					a[i][j] = 0;
				} else{
					tx = i, ty = j;
					a[i][j] = 0;
				}
			}
		}
		
		int ans = bfs();
		
		printf("Case #%d\n", ++kase); 
		if(ans != INF) printf("minimum time = %d sec\n", ans);
		else {
			printf("destination not reachable\n");
		}
	}
	return 0;
}