binary-search-tree/red-black-tree

import assert from 'assert';

import BLACK from '../color/BLACK.js';
import RED from '../color/RED.js';
import Node from '../types/Node.js';

import insert_case1 from './insert_case1.js';

/**
 * Preconditions:
 *   - n is red.
 *   - n's children are BLACK
 *
 * @param {Node} n - The input node.
 * @return {Node} The root of the modified subtree.
 */
const insert_case0 = (n) => {
    assert(n instanceof Node);
    assert(n._color === RED);
    assert(n.left._color === BLACK);
    assert(n.right._color === BLACK);
    /**
     * If n is the root of the tree, paint it black and we are done.
     *
     *      >R
     *      / \
     *     -   -
     */
    if (n.parent === null) {
        n._color = BLACK;
        return n;
    }

    return insert_case1(n);
};

export default insert_case0;