AdventOfCode/18

class Node {
    constructor(content, parent, is_right) {
        if (content === undefined) return;
        this._parent = parent;
        if (typeof content === 'number') return this._value = content;
        this._left = new Node(content[0], this, false);
        this._right = new Node(content[1], this, true);
    }

    get is_right() {
        return this.parent.right === this;
    }

    get is_left() {
        return this.parent.left === this;
    }

    get parent() {
        return this._parent;
    }

    get value() {
        return this._value === undefined ? -1 : this._value;
    }

    get left() {
        return this._left;
    }

    get right() {
        return this._right;
    }

    get depth() {
        if (!this.parent) return 0;
        return this.parent.depth + 1;
    }

    _search_number(searched_side) {
        var other_side = searched_side === 'right' ? 'left' : 'right';
        if (this['is_' + other_side] && this.parent[searched_side].value !== -1) return this.parent[searched_side];
        var t = this;
        var switched_edge = false;
        do {
            if (switched_edge) {
                t = t[other_side];
            } else if (t['is_' + searched_side]) {
                t = t.parent;
                if (!t.parent) return;
            } else {
                switched_edge = true;
                t = t.parent[searched_side];
            }
        } while (t.value === -1);
        return t;
    }

    get number_right() {
        return this._search_number('right');
    }

    get number_left() {
        return this._search_number('left');
    }

    get magnitude() {
        if (this.value !== -1) return this.value;
        return this.left.magnitude * 3 + this.right.magnitude * 2;
    }

    reduce() {
        while (this.explode() || this.split());
        return this;
    }

    explode() {
        if (this.value !== -1 || this.depth !== 4) {
            return !!this.left?.explode() || !!this.right?.explode();
        }
        var left = this.left.number_left;
        if (left) left.add(this.left.value);
        var right = this.right.number_right;
        if (right) right.add(this.right.value);
        this._right = null;
        this._left = null;
        this._value = 0;
        return true;
    }

    split() {
        if (this.value < 10) {
            return !!this.left?.split() || !!this.right?.split();
        }
        this._left = new Node(Math.floor(this.value / 2), this, false);
        this._right = new Node(Math.ceil(this.value / 2), this, true);
        this._value = undefined;
        return true;
    }

    add(amount) {
        this._value += amount;
    }

    toString() {
        return this.toArray().toString();
    }

    toArray() {
        return this.value !== -1 ? this.value : [ this.left.toArray(), this.right.toArray() ];
    }

    concat(node) {
        this._parent = new Node();
        node._parent = this._parent;
        this._parent._left = this;
        this._parent._right = node;
        return this._parent;
    }
}

export function execute(input_data) {
    var input = input_data.split('\n').map(t => new Node(JSON.parse(t)));
    var max = [];
    for (var i = 0; i < input.length; i++) {
        for (var j = 0; j < input.length; j++) {
            if (i !== j) {
                var t1 = new Node(input[i].toArray());
                var t2 = new Node(input[j].toArray());
                var r = t1.concat(t2).reduce().magnitude;
                if (r > max) max = r;
            }
        }
    }
    return [
        input.slice(1).reduce((a, b) => a.concat(b).reduce(), input[0]).magnitude,
        max
    ];
}