CodeCombat: Black Diamond Solution

coco.black.diamond.js

// track positions for safe route back to center
var positionStack = [];

// track last target, to determine changes
var lastTarget    = { x: 40, y: 34 };

loop {
    var gem = this.findNearest(this.findItems());
    
    if (gem) {
        // The isPathClear method tells you if there’s an obstacle in the way.
        var clear = this.isPathClear(this.pos, gem.pos);
        
        if (clear) {
            // If it’s clear, move() to gem.pos.
            this.move(gem.pos);
            
            // When we head towards a new gem, place the previous
            // location onto the positionStack for safe travel back.
            if ( gem.pos != lastTarget ) {
                positionStack.push( lastTarget );
                lastTarget = gem.pos;
            }
        } else {
            // Else, move back to the center point.
            // Use the positionStack to travel back to center.
            while ( positionStack.length > 0 ) {
                var pos = positionStack.pop();
                this.moveXY(pos.x, pos.y);
            }
            
            // Always put the center location back onto the stack.
            lastTarget = { x: 40, y: 34 };
        }
    }
}