web/wavl.js

class WAVLTree extends AVLTree {
    isCorrectNode(node, recursive) {
        if (!node) {
            return true;
        }

        nodeDifferences(node).forEach(childRank => {
            if ([1, 2].findIndex(childRank) == -1) {
                return false;
            }
        });

        if (node.type() == LEAF) {
            return node.rank == 0;
        }

        return !(recursive ?? true) || (this.isCorrectNode(node.left) && this.isCorrectNode(node.right));
    }

    fixDelete(x, y, z, reversed, rotateLeft, rotateRight) {
        let newRoot = x;
        let [v, w] = [y.left, y.right];

        if (reversed) {
            [v, w] = [w, v];
        }

        let wDiff = nodeDifference(w, y);

        if (wDiff == 1 && y.parent) {
            newRoot = rotateLeft(y.parent);

            y.promote();
            z.demote();

            if (z.type() == LEAF) {
                z.demote();
            }
        } else if (wDiff == 2 && v && v.parent) {
            rotateRight(v.parent);
            newRoot = rotateLeft(v.parent);

            v.promote().promote();
            y.demote();
            z.demote().demote();
        }

        return newRoot;
    }

    bottomUpDelete(x, parent) {
        let xDiff = nodeDifference(x, parent);
        if (xDiff != 3 || !parent) {
            return;
        }

        let y = (parent.left === x) ? parent.right : parent.left;
        let yDiff = nodeDifference(y, parent);

        while (parent && xDiff == 3 && y && (yDiff == 2 || nodeDifferences(y).equals([2, 2]))) {
            parent.demote();
            if (yDiff != 2) {
                y.demote();
            }

            x = parent;
            parent = x.parent;
            if (!parent) {
                return;
            }

            let y = (parent.left === x) ? parent.right : parent.left;

            xDiff = nodeDifference(x, parent);
            yDiff = nodeDifference(y, parent);
        }

        if (!parent) {
            return;
        }

        let rotatingAroundRoot = parent.parent == null;
        let newRoot = parent;

        let parentNodeDiffs = nodeDifferences(parent);
        if (parentNodeDiffs.sort().equals([1, 3])) {
            if (parent.left === x) {
                newRoot = this.fixDelete(x, parent.right, parent, false, rotateLeft, rotateRight);
            } else {
                newRoot = this.fixDelete(x, parent.left, parent, true, rotateRight, rotateLeft);
            }
        }

        if (rotatingAroundRoot) {
            this.root = newRoot;
        }
    }

    deleteFixup(y, parent) {
        let z = (y) ? y : parent;

        if (nodeDifferences(z).equals([2, 2])) {
            z.demote();
        }

        if (!parent) {
            return;
        }

        [parent.left, parent.right].forEach(y => {
            if (nodeDifference(y, parent) == 3) {
                this.bottomUpDelete(y, parent);
            }
        });
    }

    deleteRebalance(node, parent) {
        while (node || parent) {
            this.deleteFixup(node, parent);
            [node, parent] = parent, (parent) ? parent.parent : null;
        }
    }
}