Question

I am having a problem with an algorithm I wrote for creating a ascii maze. The code is using a recursive back tracker, and the pseudo code essentially is:

1. Make the initial cell the current cell and mark it as visited
2. While there are unvisited cells
    1. If the current cell has any neighbours which have not been visited
        1. Choose randomly one of the unvisited neighbours
        2. Push the chosen cell to the stack
        3. Remove the wall between the current cell and the chosen cell
        4. Make the chosen cell the current cell and mark it as visited
    2. Else
        1. Pop a cell from the stack
        2.Make it the current cell

The problem that I am having is that the code is getting stuck in a loop of adding to the stack and then popping the stack. The code currently uses one system command for linux on line 19 if anyone needs to change it for a windows machine

#include<iostream>
#include<cstdlib>
#include<stack>
#include<ctime>

#define NORTH   0
#define SOUTH   1
#define EAST    2
#define WEST    3
#define SIZEX   20
#define SIZEY   20

using namespace std;

int nGood = 0;
int locX = 1, locY = 1;

void printGrid(char grid[SIZEY][SIZEX]){
system("clear");
for (int i = 0; i < SIZEY; i++){
    for(int j = 0; j < SIZEX; j++){
        cout << grid[i][j];
    }
    cout << endl;
}
}

int moveEW(int direction, int x){
    if (direction == EAST)
            return x + 1;
    else if (direction == WEST)
            return x - 1;
    else
            return x;
}

int moveNS(int direction, int y){
    if (direction == NORTH)
            return y - 1;
    else if (direction == SOUTH)
            return y + 1;
    else
            return y;
}

 bool isGood(int x, int y, int direction, char grid[SIZEY][SIZEX]){
x = moveEW(direction,x);
y = moveNS(direction,y);

if (grid[x][y] == '.' || x >= (SIZEX - 1) || x <= 0 || y <= 0 || y >= (SIZEY - 1)){
    return false;
}

// check cardinal directions
if (direction == NORTH){
    if (grid[y][x-1] != '.' &&  grid[y-1][x] != '.' && grid[y][x+1] != '.' &&  grid[y-1][x-1] != '.' && grid[y-1][x+1] != '.'){
        return true;
    }
}
if (direction == SOUTH){
            if (grid[y][x-1] != '.' &&  grid[y+1][x] != '.' && grid[y][x+1] != '.' && grid[y+1][x-1] != '.' && grid[y+1][x+1] != '.'){
                    return true;
            }
    }
if (direction == EAST){
            if (grid[y][x+1] != '.' &&  grid[y-1][x] != '.' && grid[y+1][x] != '.' && grid[y-1][x+1] != '.' && grid[y+1][x+1] != '.'){
                    return true;
            }
    }
if (direction == WEST){
            if (grid[y][x-1] != '.' &&  grid[y-1][x] != '.' && grid[y+1][x] != '.' && grid[y-1][x-1] != '.' && grid[y+1][x-1] != '.'){
                    return true;
            }
    }
return false;
}

main(){
char grid[SIZEY][SIZEX];

// init grid
for (int i = 0; i < SIZEY; i++){
            for(int j = 0; j < SIZEX; j++){
                    grid[i][j] = '#';
            }
    }

//init rand
srand(time(0));

//init stacks for xy coords
stack<int> xValues;
stack<int> yValues;

nGood = 0;
int direction = 0;

do{
    //find n good moves
    for (int i = 0; i < 4; i++){
        if (isGood(locX,locY,i,grid))
            nGood++;
    }

    // if only 1 good move, move there
    if (nGood == 1){
        if (isGood(locX,locY,NORTH,grid))
            locY = moveNS(NORTH,locY);
        else if (isGood(locX,locY,SOUTH,grid))
            locY = moveNS(SOUTH,locY);
        else if (isGood(locX,locY,EAST,grid))
                            locX = moveEW(EAST,locX);
                    else if (isGood(locX,locY,WEST,grid))
                            locX = moveEW(WEST,locX);
    }

    // if no good moves, move back in stack
    else if (nGood == 0){
        locX = xValues.top();
        locY = yValues.top();
        xValues.pop();
        yValues.pop();
    }

    //if more than 1 good move, push stack
    else if (nGood > 1){
        xValues.push(locX);
        yValues.push(locY);

        //direction to move randomly chosen
        do{
            direction = rand() % 4;
        }while (!isGood(locX,locY,direction,grid));

        locX = moveEW(direction,locX);
        locY = moveNS(direction,locY);
    }

    // set grid
    grid[locY][locX] = '.';
    //output grid to show creation
    printGrid(grid);
    //reset nGood value
            nGood = 0;

}while(!xValues.empty());

//final maze output
printGrid(grid);
return 0;
}

Answer 1

You swapped x and y in first if in isGood function (grid[x][y] instead of grid[y][x]). This causes the problem at least sometimes.