Interview Question: Merge two sorted singly linked lists without creating new nodes

Question

This is a programming question asked during a written test for an interview. \"You have two singly linked lists that are already sorted, you have to merge them and return a

Answer 1

public static Node merge(Node h1, Node h2) {

    Node h3 = new Node(0);
    Node current = h3;

    boolean isH1Left = false;
    boolean isH2Left = false;

    while (h1 != null || h2 != null) {
        if (h1.data <= h2.data) {
            current.next = h1;
            h1 = h1.next;
        } else {
            current.next = h2;
            h2 = h2.next;
        }
        current = current.next;

        if (h2 == null && h1 != null) {
            isH1Left = true;
            break;
        }

        if (h1 == null && h2 != null) {
            isH2Left = true;
            break;
        }
    }

    if (isH1Left) {
        while (h1 != null) {
            current.next = h1;
            current = current.next;
            h1 = h1.next;
        }
    } 

    if (isH2Left) {
        while (h2 != null) {
            current.next = h2;
            current = current.next;
            h2 = h2.next;
        }
    }

    h3 = h3.next;

    return h3;
}