好的，所以我开始研究这个问题http://dwite.ca/questions/shortest_path_around_v2.html，我从两个角度看待它，DFS / BFS，现在我想问为什么我的DFS / BFS都不起作用 这是我的BFS和DFS的代码，BFS也提供输出但不是最短路径，它只提供A路径
package bfsv3;
import java.util.*;
import java.io.*;
public class BFSV3 {
static int steps = 0;
static int numSteps[][] = new int[8][8];
static int finx, finy;
public static void main(String[] args) throws FileNotFoundException {
// here is my input
//........
//........
//...##...
//A..##...
//...##...
//...##...
//...##..B
//........
//and this is the output for the dfs, as you can see where B is it doesnt give 8 but 9
//3 3 3 3 4 5 6 7
//2 2 2 3 4 5 6 7
//1 1 2 # # 5 6 7
//0 1 2 # # 6 6 7
//1 1 2 # # 7 7 7
//2 2 2 # # 8 8 8
//3 3 3 # # 7 8 9
//4 4 4 4 5 6 7 8
Scanner s = new Scanner(new File("C:\\Users\\DANIEL\\Desktop\\Java\\BFSV3\\src\\bfsv3\\DATA4.txt"));
for (int q = 0; q < 5; q++) {
char[][] maze = new char[8][8];
for (int y = 0; y < 8; y++) {
String text = s.nextLine();
for (int x = 0; x < 8; x++) {
maze[x][y] = text.charAt(x);
numSteps[x][y] = 9999;
}
}
for (int z = 0; z < 8; z++) {
for (int a = 0; a < 8; a++) {
if (maze[a][z] == 'B') {
finx = a;
finy = z;
}
if (maze[a][z] == 'A') {
//System.out.println(bfs(maze, z, a, '#', 'B') - 1);
dfs(a, z, maze, 0, 'B');
}
}
}
// System.out.println(finx + " " + finy);
//System.out.println(numSteps[finx][finy]);
for (int i = 0; i < 8; i++) {
for (int a = 0; a < 8; a++) {
if (numSteps[a][i] != 9999) {
System.out.print(numSteps[a][i] + " ");
} else {
System.out.print("#" + " ");
}
}
System.out.println();
}
System.out.println("\n\n");
}
}
public static void dfs(int x, int y, char[][] maze, int steps, char target) {
if (maze[x][y] == '#') {
return;
}
//System.out.println(steps+" "+numSteps[x][y]);
numSteps[x][y] = Math.min(steps, numSteps[x][y]);
if (steps > numSteps[x][y]) {
return;
}
try {
if (x > 0) {
dfs(x - 1, y, maze, steps + 1, target);
}
if (x < 8) {
dfs(x + 1, y, maze, steps + 1, target);
}
if (y > 0) {
dfs(x, y - 1, maze, steps + 1, target);
}
if (y < 8) {
dfs(x, y + 1, maze, steps + 1, target);
}
if (x > 0 && y > 0) {
dfs(x - 1, y - 1, maze, steps + 1, target);
}
if (x > 0 && y < 8) {
dfs(x - 1, y + 1, maze, steps + 1, target);
}
if (x < 8 && y < 8) {
dfs(x + 1, y + 1, maze, steps + 1, target);
}
if (x < 8 && y > 0) {
dfs(x + 1, y - 1, maze, steps + 1, target);
}
} catch (Exception e) {
};
}
public static int bfs(char[][] maze, int yStart, int xStart, char wall, char goal) {
Queue<int[]> queue = new LinkedList<int[]>();
int[] start = {yStart, xStart, 0};
queue.add(start);
while (queue.peek() != null) {
int[] array = queue.remove();
int x = array[0];
int y = array[1];
if (x < 0 || x >= 8 || y < 0 || y >= 8) {
continue;
}
if (maze[x][y] == wall) {
continue;
}
if (maze[x][y] == goal) {
return array[2] + 1;
}
int[][] newPoints = {{0, -1}, {0, 1}, {1, 0}, {-1, 0}, {-1, -1}, {-1, 1}, {1, -1}, {1, 1}};
//int[][] newPoints = {{-1,-1},{-1,1},{1,-1},{1,1}};
for (int i = 0; i < 8; i++) {
int[] temp = {x + newPoints[i][0], y + newPoints[i][1], array[2] + 1};
queue.add(temp);
}
maze[x][y] = wall;
}
return 0;
}
}
答案 0 :(得分：1)
<强> DFS ：
您正在检查超出界限的迷宫限制。（例如 if (x < 8) ，
但是你的迷宫被宣布为 char[][] maze = new char[8][8];
这会生成java.lang.ArrayIndexOutOfBoundsException， 但是这个异常并没有被抛出，因为空的catch块：
} catch (Exception e)
{
};
在dfs方法
拜托，不要做这种事！ （Why are empty catch blocks a bad idea?）
另外，这会打破你的递归。
BFS ：我认为使用int's的辅助数组更容易理解，至少是为了测试。
无论如何，这里有你发布的代码的修改工作版本：
package rpax.stackoverflow.maze13549150;
import java.io.File;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
public class Main13549150 {
static int steps = 0;
static int numSteps[][] = new int[8][8];
static int finx, finy;
public static void main(String[] args) {
try
{
Scanner s = new Scanner(new File("files/files13549150/DATA4.txt"));
// for (int q = 0; q < 5; q++)
// { // I dont know the reason of this loop - Maybe more files?
char[][] maze = new char[8][8];
System.out.println("MAZE: ");
for (int y = 0; y < 8; y++)
{
String text = s.nextLine();
for (int x = 0; x < 8; x++)
{
maze[x][y] = text.charAt(x);
System.out.print(maze[x][y] + " ");
numSteps[x][y] = Integer.MAX_VALUE;
}
System.out.println();
}
System.out.println();
outer:
for (int z = 0; z < 8; z++)
{
for (int a = 0; a < 8; a++)
{
if (maze[a][z] == 'B')
{
finx = a;
finy = z;
}
if (maze[a][z] == 'A')
{
System.out.println("BFS: ");
System.out.println(bfs2(maze, a, z, '#', 'B'));
dfs(a, z, maze, 0, 'B');
break outer;
}
}
}
System.out.println("DFS: ");
for (int y = 0; y < 8; y++)
{
for (int x = 0; x < 8; x++)
{
if (maze[x][y] == '#')
{
System.out.print('#' + " ");
}
else
System.out.print(numSteps[x][y] + " ");
}
System.out.println();
}
}
catch (Exception e)
{
e.printStackTrace();
}
}
public static void dfs(int x, int y, char[][] maze, int steps, char target) {
if (maze[x][y] == '#')
{
return;
}
// System.out.println(steps+" "+numSteps[x][y]);
numSteps[x][y] = Math.min(steps, numSteps[x][y]);
if (steps > numSteps[x][y])
{
return;
}
// try {
if (x > 0)
{
dfs(x - 1, y, maze, steps + 1, target);
}
if (x < 7)
{
dfs(x + 1, y, maze, steps + 1, target);
}
if (y > 0)
{
dfs(x, y - 1, maze, steps + 1, target);
}
if (y < 7)
{
dfs(x, y + 1, maze, steps + 1, target);
}
if (x > 0 && y > 0)
{
dfs(x - 1, y - 1, maze, steps + 1, target);
}
if (x > 0 && y < 7)
{
dfs(x - 1, y + 1, maze, steps + 1, target);
}
if (x < 7 && y < 7)
{
dfs(x + 1, y + 1, maze, steps + 1, target);
}
if (x < 7 && y > 0)
{
dfs(x + 1, y - 1, maze, steps + 1, target);
}
// try to avoid this kind of things -> bad practice + breaks recursion
// } catch (Exception e) {
// };
}
public static int bfs2(char[][] maze, int yStart, int xStart, char wall,
char goal) {
Queue<int[]> queue = new LinkedList<int[]>();
int[] start = { yStart, xStart, 0 };
int[][] res = new int[8][8];
int distanceToGoal = Integer.MAX_VALUE;
for (int i = 0; i < res.length; i++)
{
for (int j = 0; j < res.length; j++)
{
res[i][j] = Integer.MAX_VALUE;
}
}
queue.add(start);
while (queue.peek() != null)
{
int[] array = queue.remove();
int x = array[0];
int y = array[1];
if (x < 0 || x >= 8 || y < 0 || y >= 8)
{
continue;
}
if (maze[x][y] == wall)
{
continue;
}
// already explored
if (array[2] >= res[x][y])
{
continue;
}
res[x][y] = array[2];
if (maze[x][y] == goal)
{
distanceToGoal = array[2] + 1;
break;
}
int[][] newPoints = { { 0, -1 }, { 0, 1 }, { 1, 0 }, { -1, 0 },
{ -1, -1 }, { -1, 1 }, { 1, -1 }, { 1, 1 } };
for (int i = 0; i < 8; i++)
{
int[] temp = { x + newPoints[i][0], y + newPoints[i][1],
array[2] + 1 };
queue.add(temp);
}
}
// testing
for (int i = 0; i < 8; i++)
{
for (int j = 0; j < 8; j++)
{
if (maze[j][i] == wall)
{
System.out.print("#" + " ");
}
else if (res[j][i] != Integer.MAX_VALUE)
System.out.print(res[j][i] + " ");
else // if not explored
System.out.print("." + " ");
}
System.out.println();
}
return distanceToGoal;
}
}
输出：
MAZE:
. . . . . . . .
. . . . . . . .
. . . # # . . .
A . . # # . . .
. . . # # . . .
. . . # # . . .
. . . # # . . B
. . . . . . . .
BFS:
3 3 3 3 4 5 6 7
2 2 2 3 4 5 6 7
1 1 2 # # 5 6 7
0 1 2 # # 6 6 7
1 1 2 # # 7 7 7
2 2 2 # # 7 7 .
3 3 3 # # 6 7 8
4 4 4 4 5 6 7 8
9
DFS:
3 3 3 3 4 5 6 7
2 2 2 3 4 5 6 7
1 1 2 # # 5 6 7
0 1 2 # # 6 6 7
1 1 2 # # 7 7 7
2 2 2 # # 7 7 8
3 3 3 # # 6 7 8
4 4 4 4 5 6 7 8