Method #removeNode

data_structures/binary_search_tree.ts:387–416

Removes the given node, and returns the node that was physically removed from the tree.

(
    node: BinarySearchNode<T>,
  )

  /** Removes the given node, and returns the node that was physically removed from the tree. */
  #removeNode(
    node: BinarySearchNode<T>,
  ): BinarySearchNode<T> | null {
    /**
     * The node to physically remove from the tree.
     * Guaranteed to have at most one child.
     */
    const flaggedNode: BinarySearchNode<T> | null = !node.left || !node.right
      ? node
      : node.findSuccessorNode()!;
    /** Replaces the flagged node. */
    const replacementNode: BinarySearchNode<T> | null = flaggedNode.left ??
      flaggedNode.right;

    if (replacementNode) replacementNode.parent = flaggedNode.parent;
    if (!flaggedNode.parent) {
      this.#root = replacementNode;
    } else {
      flaggedNode.parent[flaggedNode.directionFromParent()!] = replacementNode;
    }
    if (flaggedNode !== node) {
      /** Swaps values, in case value of the removed node is still needed by consumer. */
      const swapValue = node.value;
      node.value = flaggedNode.value;
      flaggedNode.value = swapValue;
    }

    this.#size--;
    return flaggedNode;
  }

  /**
   * Add a value to the binary search tree if it does not already exist in the