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 (!('dirs' in me)) {
                me.dirs = Array(map.getWidth());
                for (var i=0; i<map.getWidth(); i++) {
                    me.dirs[i] = Array(map.getHeight());
                }
                var keypos = me.findNearest('blueKey');
                var dist=0;
                var edges = [[keypos.x, keypos.y, '']];
                while (edges.length>0) {
                    var next_edges = [];
                    while (edges.length>0) {
                        var edge = edges.shift();
                        me.dirs[edge[0]][edge[1]] = {
                            'dist': dist,
                            'dir': edge[2]
                        };
            
                        var adj_cells = map.getAdjacentEmptyCells(
                            edge[0], edge[1]);
                        while (adj_cells.length>0) {
                            var cell = adj_cells.shift();
                            var x = cell[0][0];
                            var y = cell[0][1];
                            map.setSquareColor(x,y,'#020');
                            if (map.getObjectTypeAt(x,y) != 'barrier' &&
                                !(y in me.dirs[x])) {
                                next_edges.push([x,y,cell[1]]);
                            }
                        }
                    }
                    edges = next_edges;
                    dist++;
                }
            }
            
            if (me.got_key)
                me.move('down');
            else {
                var dat = me.dirs[me.getX()][me.getY()];
                if (dat.dist == 0) {
                    me.got_key = true;
                } else switch (dat.dir) {
                  case 'up':
                    me.move('down');
                    break;
                  case 'down':
                    me.move('up');
                    break;
                  case 'left':
                    me.move('right');
                    break;
                  case 'right':
                  	me.move('left');
                    break;
                }
            }
        }
    });

    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;
    }
}