递归法求解走出迷宫的所有路径。

#include <stdio.h>
#include <stdlib.h>

void visit(int, int);

int maze[9][9] = {
    {2, 2, 2, 2, 2, 2, 2, 2, 2},
    {2, 0, 0, 0, 0, 0, 0, 0, 2},
    {2, 0, 2, 2, 0, 2, 2, 0, 2},
    {2, 0, 2, 0, 0, 2, 0, 0, 2},
    {2, 0, 2, 0, 2, 0, 2, 0, 2},
    {2, 0, 0, 0, 0, 0, 2, 0, 2},
    {2, 2, 0, 2, 2, 0, 2, 2, 2},
    {2, 0, 0, 0, 0, 0, 0, 0, 2},
    {2, 2, 2, 2, 2, 2, 2, 2, 2}
};

int startI = 1, startJ = 1; // enter point
int endI = 7, endJ = 7; // out point
int success = 0;

int main(void)
{
    int i, j;
    printf("Display map:\n");
    for(i = 0; i < 9; i++) {
        for(j = 0; j < 9; j++)
            if(maze[i][j] == 2)
                printf("██");
            else
                printf("  ");
        printf("\n");
    }
    visit(startI, startJ);
    printf("Find %d paths.\n",success);
    return 0;
}

void visit(int i, int j)
{
    int m, n;
    maze[i][j] = 1;
    if(i == endI && j == endJ) {
        success++;
        printf("\nDisplay the %dth path:\n",success);
        for(m = 0; m < 9; m++) {
            for(n = 0; n < 9; n++)
                if(maze[m][n] == 2)
                    printf("██");
                else if(maze[m][n] == 1)
                    printf("◇");
                else
                    printf("  ");
            printf("\n");
        }
    }
    //find the path(order by RLDU)
    if(maze[i][j+1] == 0) visit(i, j+1);
    if(maze[i+1][j] == 0) visit(i+1, j);
    if(maze[i][j-1] == 0) visit(i, j-1);
    if(maze[i-1][j] == 0) visit(i-1, j);

    maze[i][j] = 0;
}