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) {
               if (typeof me.step === 'undefined')
            {
                me.step = 0;
                me.state = 0;
            }
            me.step ++;
            p = Math.exp(me.step * -0.005);
            if (me.getX() == map.getWidth() - 2 &&
            me.getY() == 8)
                me.state = 2;
            if (me.state == 0)
            {
            targetX = map.getWidth() - 2;
            targetY = 8;
            
            
            
            var flag = false;
            var calcDis = function(x, y) {
                return Math.abs(targetX - x) + Math.abs(targetY - y);
            };
            
            var curDis = calcDis(me.getX(), me.getY());
            
            // move randomly
            var moves = map.getAdjacentEmptyCells(me.getX(), me.getY());
            if (me.getX() == targetX && me.getY() == targetY - 1)
                me.move('down');
            else
            if (me.getX() == targetX - 1 && me.getY() == targetY)
                me.move('right');
            else
            //if (me.getX() == target
            // getAdjacentEmptyCells gives array of ((x, y), direction) pairs
            while (!flag) {
            var m = moves[map.getRandomInt(0, moves.length - 1)];
            var d = calcDis(m[0][0], m[0][1]);
            if (d<curDis || Math.random() < p)
               {
                flag = true;
                me.move(m[1]);
            } 
            }
            } else me.move('down');
            








































        }
    });

    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;
    }
}