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 targetX = map.getWidth() - 2
var targetY = 8

var m = []
for (var i = 0; i < map.getHeight(); i++) {
    m[i] = []
    for (var j = 0; j < map.getWidth(); j++) {
        m[i][j] = false
    }
}

function assignScores(x, y, score) {
    var moves = map.getAdjacentEmptyCells(x, y)
    // console.log(moves)

    for (var move of moves) {
        // console.log(move)
        var setX = x
        var setY = y

        switch (move[1]) {
            case "up":
                setY = y - 1
                break
            case "left":
                setX = x - 1
                break
            case "right":
                setX = x + 1
                break
            case "down":
                setY = y + 1
                break
        }

        if (m[setY][setX] === false || score + 1 < m[setY][setX]) {
            m[setY][setX] = score + 1
            assignScores(setX, setY, score + 1)
        }
    }
}

m[targetY][targetX] = 0
assignScores(targetX, targetY, 0)

function getDirection(x, y) {
    var min = false
    var dir = false

    if (x - 1 >= 0 && m[y][x - 1] !== false) {
        if (min === false || m[y][x - 1] < min) {
            min = m[y][x - 1]
            dir = "left"
        }
    }

    if (x + 1 < m[0].length && m[y][x + 1] !== false) {
        if (min === false || m[y][x + 1] < min) {
            min = m[y][x + 1]
            dir = "right"
        }
    }

    if (y - 1 >= 0 && m[y - 1][x] !== false) {
        if (min === false || m[y - 1][x] < min) {
            min = m[y - 1][x]
            dir = "up"
        }
    }

    if (y + 1 < m.length && m[y + 1][x] !== false) {
        if (min === false || m[y + 1][x] < min) {
            min = m[y + 1][x]
            dir = "down"
        }
    }

    console.log(dir, min)

    return dir
}

if (me.getX() == targetX && me.getY() == targetY) {
  me.move("down")
  return
}


if (me.getY() > targetY) {
  me.move("down")
  return
}

me.move(getDirection(me.getX(), me.getY()))

        }
    });

    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;
    }
}