Taking on a new challenge: solving GeeksforGeeks POTD daily and sharing my solutions! 💻🔥
The goal: sharpen problem-solving skills, level up coding, and learn something new every day. Follow my journey! 🚀

100DaysOfCode #CodingChallenge #ProblemSolving #GeeksforGeeks #DeveloperJourney

Problem:

https://www.geeksforgeeks.org/problems/add-two-numbers-represented-by-linked-lists/1

Add Number Linked Lists
Difficulty: Medium Accuracy: 34.52%

You are given the head of two singly linked lists head1 and head2 representing two non-negative integers. You have to return the head of the linked list representing the sum of these two numbers.
Note: There can be leading zeros in the input lists, but there should not be any leading zeros in the output list.

Examples:
Input:

Output: 1 -> 1 -> 2 -> 2
Explanation: Given numbers are 123 and 999. There sum is 1122.

Input:

Output: 7 -> 0
Explanation: Given numbers are 63 and 7. There sum is 70.

Constraints:
1 ≤ Number of nodes in head1, head2 ≤ 105
0 ≤ node->data ≤ 9

Solution:
class Solution:
def reverse(self, head):
prev = None
while head:
nxt = head.next
head.next = prev
prev = head
head = nxt
return prev

def addTwoLists(self, head1, head2):
    h1 = self.reverse(head1)
    h2 = self.reverse(head2)
    carry = 0
    dummy = Node(0)
    curr = dummy

    while h1 or h2 or carry:
        s = carry
        if h1:
            s += h1.data
            h1 = h1.next
        if h2:
            s += h2.data
            h2 = h2.next
        curr.next = Node(s % 10)
        curr = curr.next
        carry = s // 10

    res = self.reverse(dummy.next)

    while res and res.data == 0 and res.next:
        res = res.next

    return res