05_singlyLL_merge.py

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None


class SinglyLinkedList:
    def __init__(self):
        self.head = None

    def append(self, data):
        new_node = Node(data)

        if self.head is None:
            self.head = new_node
            return

        last_node = self.head
        while last_node.next:
            last_node = last_node.next
        last_node.next = new_node

    def prepend(self, data):
        new_node = Node(data)

        if self.head is None:
            self.head = new_node
            return

        cur_node = self.head
        self.head = new_node
        new_node.next = cur_node

    def print_list(self):
        cur_node = self.head
        while cur_node:
            print(cur_node.data)
            cur_node = cur_node.next

    def merge_sorted(self, llist):
        
        p = self.head
        q = llist.head
        s = None

        if not p:
            return q
        if not q:
            return p

        if p and q:
            if p.data <= q.data:
                s = p
                p = s.next
            else:
                s = q
                q = s.next
            new_head = s

        while p and q:
            if p.data <= q.data:
                s.next = p
                s = p
                p = s.next
            else:
                s.next = q
                s = q
                q = s.next

        if not p:
            s.next = q
        if not q:
            s.next = p
        
        return new_head
                



if __name__ == "__main__":

    llist_1 = SinglyLinkedList()
    llist_1.append(1)
    llist_1.append(5)
    llist_1.append(7)
    llist_1.append(8)
    llist_1.append(10)

    llist_2 = SinglyLinkedList()
    llist_2.append(2)
    llist_2.append(3)
    llist_2.append(4)
    llist_2.append(6)
    llist_2.append(9)

    llist_1.print_list()
    print("\n")
    llist_2.print_list()
    print("\n")

    llist_1.merge_sorted(llist_2)
    llist_1.print_list()