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为了尝试编写一个蛮力迷宫解决 C 程序,我首先编写了这个 java 程序来测试一个想法。我对 C 非常陌生,并打算在 Java 中正确完成后对其进行转换。因此,我试图远离数组列表、花哨的库等,以便更容易地转换为 C。该程序需要生成一个最短步长的单一宽度路径来解决迷宫问题。我认为我的问题可能在于分割通过每个递归传递的路径存储数组。谢谢你看这个。-乔

maze:

1 3 3 3 3 
3 3 3 3 3 
3 0 0 0 3 
3 0 3 3 3 
0 3 3 3 2 


Same maze solved by this program:
4 4 4 4 4 
4 4 4 4 4 
4 0 0 0 4 
3 0 3 3 4 
0 3 3 3 2 

数字符号在代码中解释

    public class javamaze {

static storage[] best_path;
static int best_count;
static storage[] path;

//the maze - 1 = start; 2 = finish; 3 = open path
static int maze[][] = {{1, 3, 3, 3, 3}, 
    {3, 3, 3, 3, 3},
    {0, 0, 0, 0, 3},
    {0, 0, 3, 3, 3},
    {3, 3, 3, 3, 2}};

public static void main(String[] args) {

    int count1;
    int count2;

    //declares variables used in the solve method
    best_count = 0;
    storage[] path = new storage[10000];
    best_path = new storage[10000];
    int path_count = 0;


    System.out.println("Here is the maze:");
    for(count1 = 0; count1 < 5; count1++) {
        for(count2 = 0; count2 < 5; count2++) {
            System.out.print(maze[count1][count2] + " ");   
        }                       
        System.out.println("");         
    }                       

    //solves the maze
    solve(findStart()/5, findStart()%5, path, path_count);  

    //assigns an int 4 path to the maze to visually represent the shortest path
    for(int count = 0; count <= best_path.length - 1; count++)
        if (best_path[count] != null)
            maze[best_path[count].getx()][best_path[count].gety()] = 4;

    System.out.print("Here is the solved maze\n");

    //prints the solved maze
    for(count1 = 0; count1 < 5; count1++) {
        for(count2 = 0; count2 < 5; count2++){
            System.out.print(maze[count1][count2] + " ");
        }
        System.out.print("\n");
    }
}

//finds maze start marked by int 1 - this works perfectly and isn't related to the problem
public static int findStart() {
    int count1, count2;
    for(count1 = 0; count1 < 5; count1++) {
        for(count2 = 0; count2 < 5; count2++) {
            if (maze[count1][count2] == 1)
                return (count1 * 5 + count2);
        }
    }
    return -1;
}

//saves path coordinate values into a new array
public static void save_storage(storage[] old_storage) {
    int count;
    for(count = 0; count < old_storage.length; count++) {
        best_path[count] = old_storage[count];
    }
}

//solves the maze
public static Boolean solve(int x, int y, storage[] path, int path_count) {

    //checks to see if grid squares are valid (3 = open path; 0 = wall
    if (x < 0 || x > 4) { //array grid is a 5 by 5
        //System.out.println("found row end returning false");
        return false;
    }
    if (y < 0 || y > 4) {
        //System.out.println("Found col end returning false");
        return false;
    }

    //when finding finish - records the number of moves in static int best_count
    if (maze[x][y] == 2) {
        if (best_count == 0 || best_count > path_count) {
            System.out.println("Found end with this many moves: " + path_count);
            best_count = path_count;
            save_storage(path); //copies path counting array into a new static array
        }
    }
    //returns false if it hits a wall
    if (maze[x][y] == 0)
        return false;

    //checks with previously crossed paths to prevent an unnecessary repeat in steps
    for(storage i: path) 
        if (i != null)
            if (i.getx() == x && i.gety() == y) 
                return false;

    //saves current recursive x, y (row, col) coordinates into a storage object which is then added to an array.
    //this array is supposed to fragment per each recursion which doesn't seem to - this may be the issue
    storage storespoints = new storage(x, y);
    path[path_count] = storespoints;

    //recurses up, down, right, left
    if (solve((x-1), y, path, path_count++) == true || solve((x+1), y, path, path_count++) == true ||
            solve(x, (y+1), path, path_count++) == true || solve(x, (y-1), path, path_count++) == true) {
        return true;
    }

    return false;
}
} 

//stores (x, y) aka row, col coordinate points
class storage {

private int x;
private int y;

public storage(int x, int y) {
    this.x = x;
    this.y = y;
}
public int getx() {
    return x;
}
public int gety() {
    return y;
}
public String toString() {
    return ("storage coordinate: " + x + ", " + y + "-------");
}

}
4

1 回答 1

1

这原本不是一个答案,但它逐渐演变成一个答案。老实说,我认为从 Java 开始并转向 C 是一个坏主意,因为这两种语言真的没有什么相似之处,而且你不会对自己有任何好处,因为如果你依赖 java 的任何特性,移植它会遇到严重的问题有那个 C 没有(即大多数)

也就是说,我将勾勒出一些算法 C 的东西。

支撑结构

typedef
struct Node
{
    int x, y;
    // x and y are array indices
}
Node;

typedef
struct Path
{
    int maxlen, head;
    Node * path;
    // maxlen is size of path, head is the index of the current node
    // path is the pointer to the node array
}
Path;

int    node_compare(Node * n1, Node * n2); // returns true if nodes are equal, else false

void   path_setup(Path * p, Node * n); // allocates Path.path and sets first node
void   path_embiggen(Path * p);        // use realloc to make path bigger in case it fills up
int    path_toosmall(Path * p);        // returns true if the path needs to be reallocated to add more nodes
Node * path_head(Path * p);            // returns the head node of the path
void   path_push(Path * p, Node * n);  // pushes a new head node onto the path
void   path_pop(Path * p);             // pops a node from path

您可能会将迷宫格式更改为邻接列表之类的东西。您可以将每个节点存储为一个掩码,详细说明您可以从该节点前往哪些节点。

迷宫格式

const int // these constants indicate which directions of travel are possible from a node
N = (1 << 0),       // travel NORTH from node is possible
S = (1 << 1),       // travel SOUTH from node is possible
E = (1 << 2),       // travel EAST  from node is possible
W = (1 << 3),       // travel WEST  from node is possible
NUM_DIRECTIONS = 4; // number of directions (might not be 4.  no reason it has to be)

const int
START  = (1 << 4),  // starting  node
FINISH = (1 << 5);  // finishing node

const int
MAZE_X = 4,         // maze dimensions
MAZE_Y = 4;

int maze[MAZE_X][MAZE_Y] = 
{
    {E,        S|E|W,    S|E|W,    S|W       },
    {S|FINISH, N|S,      N|START,  N|S       },
    {N|S,      N|E,      S|E|W,    N|S|W     },
    {N|E,      E|W,      N|W,      N         }
};

Node start  = {1, 2}; // position of start node
Node finish = {1, 0}; // position of end node

我的迷宫与你的不同:这两种格式并没有完全以 1:1 的比例相互映射。例如,您的格式允许更精细的移动,但我的格式允许单向路径。

请注意,您的格式明确定位墙壁。使用我的格式,墙在概念上位于不可能有路径的任何地方。我创建的迷宫有3个水平的墙和5个垂直的(并且也是封闭的,即整个迷宫周围有一堵连续的墙)

对于您的蛮力遍历,我会使用深度优先搜索。您可以通过多种方式将标志映射到方向,如下所示。由于您无论如何都要遍历每个,因此访问时间无关紧要,因此数组而不是某种更快的关联容器就足够了。

偏移映射的数据格式

// map directions to array offsets
// format is [flag], [x offset], [y offset]
int mappings[][] =
{
    {N, -1,  0},
    {S,  1,  0},
    {E,  0,  1},
    {W,  0, -1}
}

最后,您的搜索。您可以迭代或递归地实现它。我的示例使用递归。

搜索算法伪代码

int search_for_path(int ** maze, char ** visited, Path * path)
{
    Node * head = path_head(path);
    Node temp;
    int i;

    if (node_compare(head, &finish)) return 1; // found finish
    if (visited[head->x][head->y])   return 0; // don't traverse again, that's pointless

    visited[head->x][head->y] = 1;
    if (path_toosmall(path)) path_embiggen(path);

    for (i = 0; i < NUM_DIRECTIONS; ++i)
    {
        if (maze[head->x][head->y] & mappings[i][0]) // path in this direction
        {
            temp = {head->x + mappings[i][1], head->y + mappings[i][2]};
            path_push(path, &temp);
            if (search_for_path(maze, visited, path)) return 1; // something found end
            path_pop(path);
        }
    }
    return 0; // unable to find path from any unvisited neighbor
}

要调用此函数,您应该像这样设置所有内容:

调用求解器

// we already have the maze
// int maze[MAZE_X][MAZE_Y] = {...};

// make a visited list, set to all 0 (unvisited)
int visited[MAZE_X][MAZE_Y] = 
{
    {0,0,0,0},
    {0,0,0,0},
    {0,0,0,0},
    {0,0,0,0}
};

// setup the path
Path p;
path_setup(&p, &start);

if (search_for_path(maze, visited, &path))
{
    // succeeded, path contains the list of nodes containing coordinates from start to end
}
else
{
    // maze was impossible
}

值得注意的是,因为我在编辑框中写了这一切,我没有测试任何它。它可能不会在第一次尝试时起作用,并且可能需要一些摆弄。例如,除非全局声明 start 和 finish,否则会有一些问题。最好将目标节点传递给搜索函数,而不是使用全局变量。

于 2012-07-12T19:47:51.773 回答