Solution to level 17 in Untrusted: http://alex.nisnevich.com/untrusted/

untrusted-lvl17-solution.js

/***************
 * pointers.js *
 ***************
 *
 * You! How are you still alive?
 *
 * Well, no matter. Good luck getting through this
 * maze of rooms - you'll never see me or the Algorithm again!
 */

function startLevel(map) {
    function shuffle(o){ //v1.0 [http://bit.ly/1l6LGQT]
        for(var j, x, i = o.length; i; j = Math.floor(Math.random() * i),
            x = o[--i], o[i] = o[j], o[j] = x);
        return o;
    };

    map.createFromGrid(
        ['+++++++++++++++++++++++++++++++++++++++++++++',
         '++o *++++o *++++o *++++o *++++o *++++o *+++++',
         '+* @ o++*   o++*   o++*   o++*   o++*   o++++',
         '++o *++++o *++++o *++++o *++++o *++++o *+++++',
         '+++++++++++++++++++++++++++++++++++++++++++++',
         '+++++* o++++* o++++* o++++* o++++* o++++* o++',
         '++++o   *++o   *++o   *++o   *++o   *++o   *+',
         '+++++* o++++* o++++* o++++* o++++* o++++* o++',
         '+++++++++++++++++++++++++++++++++++++++++++++',
         '++o *++++o *++++o *++++o *++++o *++++o *+++++',
         '+*   o++*   o++*   o++*   o++*   o++*   o++++',
         '++o *++++o *++++o *++++o *++++o *++++o *+++++',
         '+++++++++++++++++++++++++++++++++++++++++++++',
         '+++++* o++++* o++++* o++++* o++++* o++++* o++',
         '++++o   *++o   *++o   *++o   *++o   *++o   *+',
         '+++++* o++++* o++++* o++++* o++++* o++++* o++',
         '+++++++++++++++++++++++++++++++++++++++++++++',
         '++o *++++o *++++o *++++o *++++o *++++o *+++++',
         '+*   o++*   o++*   o++*   o++*   o++* E o++++',
         '++o *++++o *++++o *++++o *++++o *++++o *+++++',
         '+++++++++++++++++++++++++++++++++++++++++++++'],
        {
            '@': 'player',
            'E': 'exit',
            '+': 'block',
            'o': 'teleporter',
            '*': 'trap',
        }, 2, 2);

    var canvas = map.getCanvasContext();

    var teleportersAndTraps = map.getDynamicObjects();
    teleportersAndTraps = shuffle(teleportersAndTraps);

    for (i = 0; i < teleportersAndTraps.length; i+=2) {
        var t1 = teleportersAndTraps[i];
        var t2 = teleportersAndTraps[i+1];

        // Point each teleporter to either another teleporter
        // or a trap
        if (t1.getType() == 'teleporter') {
            t1.setTarget(t2);
        }
        if (t2.getType() == 'teleporter') {
            t2.setTarget(t1);
        }

        // TODO find a way to remove the API docs
        // wouldn't want the 'good doctor' to find
        // out about map.getCanvasCoords()...

        function updateMax(obj) {
            if (obj.getType() == 'teleporter') {
                if (map.max) {
                    let {x,y} = map.getCanvasCoords(obj);
                    if (y > map.max.y || (y == map.max.y && x > map.max.x)) {
                        map.max = {x,y,obj};
                        return obj;
                    }
                } else {
                    let {x,y} = map.getCanvasCoords(obj);
                    map.max = {x,y,obj};
                    return obj;
                }
            }
        }
        let thing = updateMax(t1);
        thing = updateMax(t2) || thing;
        
        if (thing) {
            for (let o of teleportersAndTraps) {
                if (o.getType() == 'teleporter' && o !== thing) {
                    o.setTarget(thing);
                }
            }
        }
        /*
        if (!map.thing) {
            map.thing = 'hey'
        } else {
            map.displayChapter(map.thing);
        }
        function rand() {
            return Math.floor(256*Math.random())
        }
        let s= `rgb(${rand()},${rand()},${rand()})`;
        canvas.beginPath();
        canvas.strokeStyle = s;

        

        let {x,y} = map.getCanvasCoords(t1);
        canvas.moveTo(x,y);
        ({x,y} = map.getCanvasCoords(t2));
        canvas.lineTo(x,y);
        canvas.stroke();
        */



    }
}

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