705 - Slash Maze

题目：705 - Slash Maze

题目大意：给一个斜线迷宫，求这个迷宫是否有环，最长环的长度。

解题思路：将斜线放大三倍，用数组来储存。这样的话就不需要八个方向遍历，只需要上下左右四个方向就可以了。然后如果有遍历到数组边界的就可以认定不是环了。

#include<stdio.h>
#include<string.h>

const int N = 250;
char str[N];
int visit[N][N], map[N][N];
int w, h, t = 0, flag, cnt;

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

void change(int n) {

	for(int i = 0; i < w; i++)
		if(str[i] == '\\') {

			map[3 * n][3 * i] = 1;
			map[3 * n + 1][3 * i + 1] = 1;
			map[3 * n + 2][3 * i + 2] = 1;
		}
		else if(str[i] == '/') {

			map[3 * n][3 * i + 2] = 1;
			map[3 * n + 1][3 * i + 1] = 1;
			map[3 * n + 2][ 3 * i] = 1;
		}
}

void dfs(int x, int y) {
	
	cnt++;
	visit[x][y] = 1;
	int i, x1, y1;
	for( i = 0; i < 4; i++) {
		
		 x1 = x + dir[i][0];
		 y1 = y + dir[i][1];
		 if(x1 < 0 || x1 >= 3 * h || y1 < 0 || y1 >= 3 * w)
			 continue;
		 if(map[x1][y1] || visit[x1][y1])
			 continue;
		if(x1 == 0 || x1 == 3 * h - 1 || y1 == 0 || y1 == 3 * w -1)
			flag = 1;

			dfs(x1, y1);
	}

}

int main() {

	while(scanf("%d%d%*c", &w, &h) , w || h) {
		
		t++;
		memset(map, 0, sizeof(map));
		memset(visit, 0, sizeof(visit));
		int i, j;
		for(i = 0; i < h; i++) {

			scanf("%s", str);
			change(i);
		}

		int circle_num = 0, max = 0;
		for(i = 1; i < 3*h - 1; i++)
			for(j = 1; j < 3*w - 1; j++)
				if(!map[i][j]  && !visit[i][j]) {
					
					flag = 0;
					cnt = 0;
					dfs(i, j);
					
				if(!flag) {

					circle_num++;
					if(cnt > max)
						max = cnt;
					}
				}
			
				printf("Maze #%d:\n", t);
			if(circle_num) 
				printf("%d Cycles; the longest has length %d.\n\n", circle_num, max / 3);
			else
				printf("There are no cycles.\n\n");
	}

	return 0;
}