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Task

Generate and show a maze, using the simple Depth-first search algorithm.

Start at a random cell.
Mark the current cell as visited, and get a list of its neighbors. For each neighbor, starting with a randomly selected neighbor:
If that neighbor hasn't been visited, remove the wall between this cell and that neighbor, and then recurse with that neighbor as the current cell.


 Related tasks
 Maze solving.


function maze(x,y) {
	var n=x*y-1;
	if (n<0) {alert("illegal maze dimensions");return;}
	var horiz =[]; for (var j= 0; j<x+1; j++) horiz[j]= [],
	    verti =[]; for (var j= 0; j<x+1; j++) verti[j]= [],
	    here = [Math.floor(Math.random()*x), Math.floor(Math.random()*y)],
	    path = [here],
	    unvisited = [];
	for (var j = 0; j<x+2; j++) {
		unvisited[j] = [];
		for (var k= 0; k<y+1; k++)
			unvisited[j].push(j>0 && j<x+1 && k>0 && (j != here[0]+1 || k != here[1]+1));
	}
	while (0<n) {
		var potential = [[here[0]+1, here[1]], [here[0],here[1]+1],
		    [here[0]-1, here[1]], [here[0],here[1]-1]];
		var neighbors = [];
		for (var j = 0; j < 4; j++)
			if (unvisited[potential[j][0]+1][potential[j][1]+1])
				neighbors.push(potential[j]);
		if (neighbors.length) {
			n = n-1;
			next= neighbors[Math.floor(Math.random()*neighbors.length)];
			unvisited[next[0]+1][next[1]+1]= false;
			if (next[0] == here[0])
				horiz[next[0]][(next[1]+here[1]-1)/2]= true;
			else 
				verti[(next[0]+here[0]-1)/2][next[1]]= true;
			path.push(here = next);
		} else 
			here = path.pop();
	}
	return {x: x, y: y, horiz: horiz, verti: verti};
}
 
function display(m) {
	var text= [];
	for (var j= 0; j<m.x*2+1; j++) {
		var line= [];
		if (0 == j%2)
			for (var k=0; k<m.y*4+1; k++)
				if (0 == k%4) 
					line[k]= '+';
				else
					if (j>0 && m.verti[j/2-1][Math.floor(k/4)])
						line[k]= ' ';
					else
						line[k]= '-';
		else
			for (var k=0; k<m.y*4+1; k++)
				if (0 == k%4)
					if (k>0 && m.horiz[(j-1)/2][k/4-1])
						line[k]= ' ';
					else
						line[k]= '|';
				else
					line[k]= ' ';
		if (0 == j) line[1]= line[2]= line[3]= ' ';
		if (m.x*2-1 == j) line[4*m.y]= ' ';
		text.push(line.join('')+'\r\n');
	}
	return text.join('');
}