迷宫 2D 递归算法问题

Question

我一直在尝试编写一个可以递归解决迷宫的程序。但是我的算法方法中的递归有问题。该算法最多只能求解一个位置的解。

这是控制台上的：

注意二维数组的“字符指示符”：

'*' = 墙壁
'#' = 开始
'$'=结束
' '=可能path/not一堵墙
'@'=路径
'~' = 死胡同

期望的输出：

Presolved maze:
* * * * * * * * * * 
* # * * * * * * * * 
*   *           * * 
*   *       *   * * 
*       *   *   * * 
* * *       *   * * 
* *     *   *   * * 
* *     *   *     * 
* * * * * * *     * 
*               $ * 
* * * * * * * * * * 

Maze solution:

* * * * * * * * * * 
* # * * * * * * * * 
* @ * @ @ @ @ @ * * 
* @ * @ ~ ~ * @ * * 
* @ @ @ * ~ * @ * * 
* * * ~ ~ ~ * @ * * 
* * ~ ~ * ~ * @ * * 
* * ~ ~ * ~ * @ ~ * 
* * * * * * * @ ~ * 
* ~ ~ ~ ~ ~ ~ @ $ * 
* * * * * * * * * *

我得到的输出：

Presolved maze:
* * * * * * * * * * 
* # * * * * * * * * 
*   *           * * 
*   *       *   * * 
*       *   *   * * 
* * *       *   * * 
* *     *   *   * * 
* *     *   *     * 
* * * * * * *     * 
*               $ * 
* * * * * * * * * * 

Maze solution:

* * * * * * * * * * 
* # * * * * * * * * 
* @ *           * * 
*   *       *   * * 
*       *   *   * * 
* * *       *   * * 
* *     *   *   * * 
* *     *   *     * 
* * * * * * *     * 
*               $ * 
* * * * * * * * * *

我已经尝试过其他解决方案，例如在我的一般情况下删除递归内的递归，但这只是倒退了我的算法可以做的小进步（找到一个位置）。我想知道我还能做些什么来解决这个问题？其他方法有效，但“算法”方法并不像我希望的那样有效。

import java.util.*;
public class maze {
    public static void main(String[] args) {
        allocateMaze();
    }
    
    public static void allocateMaze() {
        char[][] mazeArr = {{'*','*','*','*','*','*','*','*','*','*'},//0
                            {'*','#','*','*','*','*','*','*','*','*'},//1
                            {'*',' ','*',' ',' ',' ',' ',' ','*','*'},//2
                            {'*',' ','*',' ',' ',' ','*',' ','*','*'},//3
                            {'*',' ',' ',' ','*',' ','*',' ','*','*'},//4
                            {'*','*','*',' ',' ',' ','*',' ','*','*'},//5
                            {'*','*',' ',' ','*',' ','*',' ','*','*'},//6
                            {'*','*',' ',' ','*',' ','*',' ',' ','*'},//7
                            {'*','*','*','*','*','*','*',' ',' ','*'},//8
                            {'*',' ',' ',' ',' ',' ',' ',' ','$','*'},//9
                            {'*','*','*','*','*','*','*','*','*','*'}};//10
        
        //setting row and col to 0 for display method
        int row = 0;
        int col = 0;
        System.out.println("Presolved maze:");
        displayMaze(mazeArr, row, col); //displays presolved maze
        row = 1;
        col = 1;
        boolean isSolved = false;
        System.out.println("\nMaze solution:");
        algorithm(mazeArr, row, col, isSolved); //create variable for solved maze, sends maze allocation to method that solves the maze
        System.out.println();
        row = 0;
        col = 0;
        displayMaze(mazeArr, row, col); //displays traced + solved maze
    }

    public static void displayMaze(char[][] mazeArr, int row, int col) {
        if (row < mazeArr.length) { //iterate through all (11) rows
            if (col < mazeArr[row].length) { //iterate through all (11) columns
                System.out.print(mazeArr[row][col] + " "); //displays the current index in the array
                displayMaze(mazeArr, row, col+1); //repeats this method by iterating through the columns first
                return;
            }
            System.out.println(); //enters the line after each row for display purposes
            displayMaze(mazeArr, row+1, col=0); //repeats this method by iterating through the rows
        }
    }
    
    public static char[][] algorithm(char[][] mazeArr, int row, int col, boolean isSolved){
        boolean isPath = false; // assume there is no path

        if (mazeArr[row][col] == '$' && isSolved == true) { // IF MAZE IS COMPLETELY SOLVED
            return mazeArr;

        } else { // IF MAZE IS NOT COMPLETELY SOLVED
            
            if (isSolved == false && isPath == false) { // start searching thru the maze, assume there is no path
                // THERE IS NO DEAD END
                
                if (mazeArr[row - 1][col] == ' ') { // if north has a path
                    mazeArr[row - 1][col] = '@'; // block off path to not go back here again
                    isPath = true; // there is a path
                    isSolved = false; // assume maze is still not solved
                    
                    return algorithm(mazeArr, row--, col, isSolved); // repeat process going to next north spot
                }
                
                if (mazeArr[row][col + 1] == ' ') { // if east has a path
                    mazeArr[row][col + 1] = '@'; // block off path to not go back here again
                    isPath = true; // there is a path
                    isSolved = false; // assume maze is still not solved

                    return algorithm(mazeArr, row, col++, isSolved); // repeat process going to next east spot
                }
                
                if (mazeArr[row + 1][col] == ' ') { // if south has a path
                    mazeArr[row + 1][col] = '@'; // block off path to not go back here again
                    isPath = true; // there is a path
                    isSolved = false; // assume maze is still not solved
                    
                    return algorithm(mazeArr, row++, col, isSolved); // repeat process going to next south spot
                }
                
                if (mazeArr[row][col - 1] == ' ') { // if west has a path
                    mazeArr[row][col - 1] = '@'; // block off path to not go back here again
                    isPath = true; // there is a path
                    isSolved = false; // assume maze is still not solved
                    
                    return algorithm(mazeArr, row, col--, isSolved); // repeat process going to next west spot
                }
                
                if (mazeArr[row][col] == '$') { // if you have reached the end of the maze
                    isSolved = true; // maze has been solved
                    
                    
                    return algorithm(mazeArr, row, col, isSolved); // algorithm will recognize
                }

            } else { // finds alternate path if there's a dead end
                if (mazeArr[row][col] != '#') {
                mazeArr[row][col] = '~'; //indicates that this index is a dead end
                }
                
                if (isPath == false) {
                    if (mazeArr[row - 1][col] == '@' && mazeArr[row - 1][col] != '#') { // if north was a path
                        isPath = true; 
                        isSolved = false;
                        
                        return algorithm(mazeArr, row--, col, isSolved); //returns to initial position before hitting dead end
                    }
                }
                
                if (isPath == false) {
                    if (mazeArr[row][col+1] == '@' && mazeArr[row][col+1] != '#') { // if east was a path
                        isPath = true; 
                        isSolved = false;
                        
                        return algorithm(mazeArr, row, col++, isSolved); //returns to initial position before hitting dead end
                    }
                }
                
                if (isPath == false) {
                    if (mazeArr[row + 1][col] == '@' && mazeArr[row + 1][col] != '#') { // if south was a path
                        isPath = true; 
                        isSolved = false;
                        
                        return algorithm(mazeArr, row++, col, isSolved); //returns to initial position before hitting dead end
                    }
                }
                
                if (isPath == false) {
                    if (mazeArr[row][col-1] == '@' && mazeArr[row][col-1] != '#') { // if west was a path
                        isPath = true; 
                        
                        return algorithm(mazeArr, row, col--, isSolved); //returns to initial position before hitting dead end
                    }
                }
                
                if (isPath == false) { // if there's no way out, that means there is no solution
                    System.out.println("No Solution");              
                    return mazeArr;
                }
                
            }
            return mazeArr;
        }
    }
}

Answer 1

记得algorithm()时，需要在row或col之前加上++或--。当其中之一出现在变量之后时，变量会增加，但不会增加输出的值：

public class Test {
    public static void main(String[] args) {
        int x = 5;
        int y = x++;
        System.out.println(x + " " + y);
    }
}

给予

6 5

以上 x++ 递增 x，但 y 之前设置为 x 的值。要修复它，请将增量放在变量之前，例如 ++row:

public class Test {
    public static void main(String[] args) {
        int x = 5;
        int y = ++x;
        System.out.println(x + " " + y);
    }
}

输出：

6 6

迷宫 2D 递归算法问题

Maze 2D Recursive Algorithm Issue

java

algorithm

recursion

maze