👉🏻题目链接：
🚀https://www.lanqiao.cn/problems/602/learning/🚀
程序填空—迷宫：
???
01010101001011001001010110010110100100001000101010 00001000100000101010010000100000001001100110100101 01111011010010001000001101001011100011000000010000 01000000001010100011010000101000001010101011001011 00011111000000101000010010100010100000101100000000 11001000110101000010101100011010011010101011110111 00011011010101001001001010000001000101001110000000 10100000101000100110101010111110011000010000111010 00111000001010100001100010000001000101001100001001 11000110100001110010001001010101010101010001101000 00010000100100000101001010101110100010101010000101 11100100101001001000010000010101010100100100010100 00000010000000101011001111010001100000101010100011 10101010011100001000011000010110011110110100001000 10101010100001101010100101000010100000111011101001 10000000101100010000101100101101001011100000000100 10101001000000010100100001000100000100011110101001 00101001010101101001010100011010101101110000110101 11001010000100001100000010100101000001000111000010 00001000110000110101101000000100101001001000011101 10100101000101000000001110110010110101101010100001 00101000010000110101010000100010001001000100010101 10100001000110010001000010101001010101011111010010 00000100101000000110010100101001000001000000000010 11010000001001110111001001000011101001011011101000 00000110100010001000100000001000011101000000110011 10101000101000100010001111100010101001010000001000 10000010100101001010110000000100101010001011101000 00111100001000010000000110111000000001000000001011 10000001100111010111010001000110111010101101111000
???
- 迷宫问题可以使用Excel大法，将迷宫复制到表格中手动走一遍。
- 如果是常规解法这道题主要考察JavaIO与BFS的模板。
- 用DFS走迷宫运行时间很长，跑不出来；而且题目要求迷宫的解要满足字典序最小，使用BFS更方便。题目属于简单题，在BFS模板的基础上设置好行走顺序，跑一遍模板就ok了。
BFS模板可以参考这篇文章：
【蓝桥杯Java组】刷了这五道题不信你还不会BFS（广度优先搜索） - 30行50列的迷宫如果手动输入大概率会出错，需要从txt文本文件中使用IO流读数据。
🍦AC代码（Java）：
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.Deque;
import java.util.LinkedList;
//结点用来记录状态
class Node {
// 坐标
int x;
int y;
// 走迷宫的路径
StringBuilder path;
Node(int x, int y, StringBuilder path) {
this.x = x;
this.y = y;
this.path = path;
}
}
public class Main {
public static final int n = 30;
public static final int m = 50;
public static char[][] maze = new char[n][m];
public static boolean[][] vis = new boolean[n][m];
// 按照字典序设置行走顺序
public static int[][] dir = new int[][]{
{1, 0}, {0, -1}, {0, 1}, {-1, 0}
};
public static char[] go = new char[]{'D', 'L', 'R', 'U'};
public static boolean inMaze(int x, int y) {
return 0 <= x && x < n && 0 <= y && y < m;
}
// bfs模板，方法结束时就是最短路径，根据设置的顺序走，路径字典序也为最小
public static String bfs(int sx, int sy) {
Deque<Node> que = new LinkedList<>();
que.add(new Node(sx, sy, new StringBuilder("")));
vis[sx][sy] = true;
while (!que.isEmpty()) {
Node curr = que.pop();
if (curr.x == n - 1 && curr.y == m - 1) {
return curr.path.toString();
}
// 尝试向四个方向走，并记录路径
for (int i = 0; i < 4; i++) {
int tx = curr.x + dir[i][0];
int ty = curr.y + dir[i][1];
if (inMaze(tx, ty) && !vis[tx][ty] && maze[tx][ty] != '1') {
vis[tx][ty] = true;
// 这里千万不要写成StringBuilder tempPath = curr.path
// Java中这样写，tempPath指向的一直是是内存中同一个字符串
StringBuilder tempPath = new StringBuilder(curr.path);
tempPath.append(go[i]);
que.offer(new Node(tx, ty, tempPath));
}
}
}
return "";
}
public static void main(String[] args) throws IOException {
// 通过IO读取题目样例
File file = new File("E:\\test.txt");
FileReader fr = new FileReader(file);
for (int i = 0; i < 30; i++) {
for (int j = 0; j <= 51; j++) {
int ch = fr.read();
// 处理每行末尾的换行，Windows下换行符是/r/n，要读取两次
if (j == 50 || j == 51)
continue;
maze[i][j] = (char) ch;
}
}
String ans = bfs(0, 0);
System.out.println(ans);
}
}
?结果：?
DDDDRRURRRRRRDRRRRDDDLDDRDDDDDDDDDDDDRDDRRRURRUURRDDDDRDRRRRRRDRRURRDDDRRRRUURUUUUUUULULLUUUURRRRUULLLUUUULLUUULUURRURRURURRRDDRRRRRDDRRDDLLLDDRRDDRDDLDDDLLDDLLLDLDDDLDDRRRRRRRRRDDDDDDRR
