data-structures-and-algorithms/skip-list

import assert from 'assert';

const searchTopMost = (compare, node, key) => {
    // eslint-disable-next-line no-constant-condition
    while (true) {
        assert(node !== null);
        if (node.right === null) {
            if (node.down === null) {
                return null;
            }

            node = node.down;
        } else {
            const d = compare(key, node.right.key);
            if (d === 0) {
                assert(node.right.up === null);
                return node.right;
            }

            if (d > 0) node = node.right;
            else {
                if (node.down === null) {
                    return null;
                }

                node = node.down;
            }
        }
    }
};

export default searchTopMost;