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 d = ['right', 'down', 'left', 'up'],
                x = me.getX(), y = me.getY(),
                _ = [], // already traversed this cell
                tx = map.getWidth() - 2, // target x
                ty = 7; // target y
            
            hasTraversed = function(x, y) {
                for (var j = 0; j < _.length; j++)
                    if (_[j][0] == x && _[j][1] == y)
                        return true;
                return false;
            },
            
            discover = function(x, y, c) {
                var s = [],
                    e = map.getAdjacentEmptyCells(x, y);
                _.push([x, y]);
                // find possible steps
                for (var i = 0; i < e.length; i++) {
                    if (e[i][0][0] == tx && e[i][0][1] == ty) {
                        return [{ f: 1, d: e[i][1] }];
                    } else {
                        if (!hasTraversed(e[i][0][0], e[i][0][1])) {
                            s.push({ 
                                x: e[i][0][0], 
                                y: e[i][0][1],
                                d: e[i][1],
                                f: 0
                            });
                        }
                    }
                }
                // now discover what happens at the next step
                for (var i = 0; i < s.length; i++) {
                    var u = discover(s[i].x, s[i].y, c+1);
                    for(var j = 0; j < u.length; j++) {
                        if (u[j].f) {
                            s[i].f = 1;
                            return [s[i]];
                        } else {
                        
                        }    
                    }
                }
                return s;
            };
            if (me.getX() == tx && me.getY() > ty - 2) {
                me.move('down');
            } else {
                next = discover(x, y, 0);
                me.move(next[0].d);
            }
            
        }
    });

    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;
    }
}