Add Two Number Linked List Problem GFG

 Given the head of two singly linked lists num1 and num2 representing two non-negative integers. The task is to return the head of the linked list representing the sum of these two numbers.


For example, num1 represented by the linked list : 1 -> 9 -> 0, similarly num2 represented by the linked list: 2 -> 5. Sum of these two numbers is represented by 2 -> 1 -> 5.


Note: There can be leading zeros in the input lists, but there should not be any leading zeros in the output list.


Examples:


Input: num1 = 4 - > 5, num2 = 3 -> 4 -> 5

Output:  3 -> 9 -> 0

 

Explanation: Given numbers are 45 and 345. There sum is 390.

Input: num1 = 0 -> 0 -> 6 -> 3, num2 = 0 -> 7 

Output: 7 -> 0 

 

Explanation: Given numbers are 63 and 7. There sum is 70.

Constraints:

1 <= size of both linked lists <= 106

0 <= elements of both linked lists <= 9





class Solution {

    // Function to reverse a linked list

    static Node reverseNode(Node head) {

        Node prev = null;

        Node curr = head;

        Node next = null;


        while (curr != null) {

            next = curr.next;  // Store next node

            curr.next = prev;   // Reverse the link

            prev = curr;        // Move prev forward

            curr = next;        // Move curr forward

        }

        return prev;

    }


    static Node addTwoLists(Node num1, Node num2) {

        // Reverse both linked lists

        num1 = reverseNode(num1);

        num2 = reverseNode(num2);


        Node dummyHead = new Node(0);

        Node tail = dummyHead;

        int carry = 0;


        while (num1 != null || num2 != null || carry > 0) {

            int x = (num1 != null) ? num1.data : 0;

            int y = (num2 != null) ? num2.data : 0;

            int sum = x + y + carry;


            carry = sum / 10;

            tail.next = new Node(sum % 10);

            tail = tail.next;


            if (num1 != null) num1 = num1.next;

            if (num2 != null) num2 = num2.next;

        }


       

        // Step 3: Reverse the result list

        Node result = reverseNode(dummyHead.next);


        // Step 4: Remove leading zeros (if any)

        while (result != null && result.data == 0) {

            result = result.next;

        }


        return (result == null) ? new Node(0) : result;

    }

}

Comments

Post a Comment

Popular posts from this blog

Two Sum II - Input Array Is Sorted

 Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order , find two numbers such that they add up to a specific target number. Let these two numbers be numbers[index1] and numbers[index2] where 1 <= index1 < index2 <= numbers.length. Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2. The tests are generated such that there is exactly one solution. You may not use the same element twice. Your solution must use only constant extra space .   Example 1: Input: numbers = [2,7,11,15], target = 9 Output: [1,2] Explanation: The sum of 2 and 7 is 9. Therefore, index1 = 1, index2 = 2. We return [1, 2]. Example 2: Input: numbers = [2,3,4], target = 6 Output: [1,3] Explanation: The sum of 2 and 4 is 6. Therefore index1 = 1, index2 = 3. We return [1, 3]. Example 3: Input: numbers = [-1,0], target = -1 Output: [1,2] Explanation: The sum of -1 and 0 is -1. Therefore index1 = 1,...
Read more

Comparable Vs. Comparator in Java

  In Java , Comparable and Comparator both are interfaces used to sort objects. Comparable It defines  natural ordering  within a class. It is implemented  inside  the class being sorted. It uses the compareTo() method. It allows sorting  by one one . Comparable provides a  single sorting sequence . In other words, we can sort the collection on the basis of a single element such as id, name, and price. Comparable  affects the original class , i.e., the actual class is modified. Comparable is present in  java.lang  package. We can sort the list elements of Comparable type by  Collections.sort(List)  method. Only one compareTo() method can be implemented, restricting flexibility. Comparator It defines  custom sorting logic It is implemented  in a separate class  or using lambda expressions . It uses the compare() method. It allows sorting  by multiple criteria . The Comparator provides  multiple sorting...
Read more

Increasing Triplet Subsequence

 Given an integer array nums, return true if there exists a triple of indices (i, j, k) such that i < j < k and nums[i] < nums[j] < nums[k]. If no such indices exists, return false.   Example 1: Input: nums = [1,2,3,4,5] Output: true Explanation: Any triplet where i < j < k is valid. Example 2: Input: nums = [5,4,3,2,1] Output: false Explanation: No triplet exists. Example 3: Input: nums = [2,1,5,0,4,6] Output: true Explanation: The triplet (3, 4, 5) is valid because nums[3] == 0 < nums[4] == 4 < nums[5] == 6. Brute Force : Failed for some testcase class Solution {     public boolean increasingTriplet ( int [] nums ) {         int n = nums . length ;         int i = 0 ;         int j =i+ 1 ;         int k =j+ 1 ;         while (i <n && j<n && k<n)         {         if (nums...
Read more