Solution to level 13 in Untrusted: http://alex.nisnevich.com/untrusted/

untrusted-lvl13-solution.js

/*
 * robotMaze.js
 *
 * The blue key is inside a labyrinth, and extracting
 * it will not be easy.
 *
 * It's a good thing that you're a AI expert, or
 * we would have to leave empty-handed.
 */

function startLevel(map) {
    // Hint: you can press R or 5 to "rest" and not move the
    // player, while the robot moves around.

    map.getRandomInt = function(min, max) {
        return Math.floor(Math.random() * (max - min + 1)) + min;
    }

    map.placePlayer(map.getWidth()-1, map.getHeight()-1);
    var player = map.getPlayer();

    map.defineObject('robot', {
        'type': 'dynamic',
        'symbol': 'R',
        'color': 'gray',
        'onCollision': function (player, me) {
            me.giveItemTo(player, 'blueKey');
        },
        'behavior': function (me) {
  			var table = []
            for (x = 0; x < map.getWidth(); x++) {
            	table[x] = []
                for (y = 0; y < 11; y++) {
                	table[x][y] = map.getObjectTypeAt(x,y) == 'empty'
                }
            }
            table[map.getWidth()-2][8] = true; // blue key
            table[map.getWidth()-2][9] = true; // door
                        
            function cost(px, py, pc, x,y) {
            	if (typeof table[x][y] == "number" && table[x][y] < pc) {
                	pc = table[x][y];
                } else {
            		table[x][y] = pc;
                }
                //console.log("cost for ",x,y,": ",pc)
                function valid(x,y) {
                	return (x != px || y != py) && table[x] && table[x][y] == true
                }
                function recurse(i,j) {
                	if (valid(i,j)) {cost(x, y, pc+1, i, j)}
                }
                recurse(x+1, y);
                recurse(x-1, y);
                recurse(x, y+1);
                recurse(x, y-1);
           	}
            cost(map.getWidth()-2, 7, 0, map.getWidth()-2, 8);
            
            function move_if_cheap(x,y, name) {
            	var cur = table[me.getX()][me.getY()];
                var next = table[x+me.getX()][y+me.getY()];
            	if (typeof next == "number" && cur > next) {
                	console.log("Successful move towards: ",name,next);
                	me.move(name);
                    return true;
                }
                console.log("Failed move towards: ",name)
                return false;
           	}
            
            function move_mindlessly() {
            	if (me.getX() == map.getWidth()-2 && me.getY() > 7) {
                	me.move('down');
                    return true;
                }
                return false;
            }
               	
            console.log("Trying to move from ", table[me.getX()][me.getY()]);
            move_mindlessly() ||
            move_if_cheap(1,0, "right") ||
            move_if_cheap(-1,0, "left") ||
            move_if_cheap(0,1, "down") ||
            move_if_cheap(0,-1, "up");
        }
    });

    map.defineObject('barrier', {
        'symbol': '░',
        'color': 'purple',
        'impassable': true,
        'passableFor': ['robot']
    });

    map.placeObject(0, map.getHeight() - 1, 'exit');
    map.placeObject(1, 1, 'robot');
    map.placeObject(map.getWidth() - 2, 8, 'blueKey');
    map.placeObject(map.getWidth() - 2, 9, 'barrier');

    var autoGeneratedMaze = new ROT.Map.DividedMaze(map.getWidth(), 10);
    autoGeneratedMaze.create( function (x, y, mapValue) {
        // don't write maze over robot or barrier
        if ((x == 1 && y == 1) || (x == map.getWidth() - 2 && y >= 8)) {
            return 0;
        } else if (mapValue === 1) { //0 is empty space 1 is wall
            map.placeObject(x,y, 'block');
        } else {
            map.placeObject(x,y,'empty');
        }
    });
}

function validateLevel(map) {
    map.validateExactlyXManyObjects(1, 'exit');
    map.validateExactlyXManyObjects(1, 'robot');
    map.validateAtMostXObjects(1, 'blueKey');
}

function onExit(map) {
    if (!map.getPlayer().hasItem('blueKey')) {
        map.writeStatus("We need to get that key!");
        return false;
    } else {
        return true;
    }
}