00002. Merge_Sorted_Linked_list.py

#!/bin/python3

import math
import os
import random
import re
import sys

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

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

    def insert_node(self, node_data):
        node = SinglyLinkedListNode(node_data)

        if not self.head:
            self.head = node
        else:
            self.tail.next = node


        self.tail = node

def print_singly_linked_list(node, sep, fptr):
    while node:
        fptr.write(str(node.data))

        node = node.next

        if node:
            fptr.write(sep)

# Complete the mergeLists function below.

#
# For your reference:
#
# SinglyLinkedListNode:
#     int data
#     SinglyLinkedListNode next
#
#
def mergeLists(head1, head2):
    dummyNode = SinglyLinkedListNode(0) 
    temp = dummyNode  
    
    
    if head1 == None:
        return head2
    if head2 == None:
        return head1
    
        
    while head1 and head2 :  
        if head1.data <= head2.data:
            temp.next = SinglyLinkedListNode(head1.data)
            head1 = head1.next
        else:
            temp.next = SinglyLinkedListNode(head2.data)
            head2 = head2.next

        temp = temp.next    

    if head1 == None:
        temp.next = head2
    if head2 == None:
        temp.next = head1
        
    return dummyNode.next

def check_answers(file1, file2):
    i = 1
    for a,b in zip(file1.readlines(),file2.readlines()):
        if a!=b:
            print(f"Index {i} has different answers")
        i += 1


if __name__ == '__main__':
    fptr = open("output.txt", 'w')
    expected_out = open("expected_output.txt", 'r')
    input_file = open("input.txt", 'r')

    tests = int(input_file.readline())
    for tests_itr in range(tests):
        llist1_count = int(input_file.readline())

        llist1 = SinglyLinkedList()

        for _ in range(llist1_count):
            llist1_item = int(input_file.readline())
            llist1.insert_node(llist1_item)
            
        llist2_count = int(input_file.readline())

        llist2 = SinglyLinkedList()

        for _ in range(llist2_count):
            llist2_item = int(input_file.readline())
            llist2.insert_node(llist2_item)

        llist3 = mergeLists(llist1.head, llist2.head)

        print_singly_linked_list(llist3, ' ', fptr)
        fptr.write('\n')


    fptr.close()

    f1 = open("output.txt", 'r')
    f2 = open("expected_output.txt", 'r')
    check_answers(f1,f2)