LeetCode: Add Two Numbers

 Problem statement is copy pasted from Leetcode as it is:

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

 

Example 1:

Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [7,0,8]
Explanation: 342 + 465 = 807.

Example 2:

Input: l1 = [0], l2 = [0]
Output: [0]

Example 3:

Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
Output: [8,9,9,9,0,0,0,1]

 

Constraints:

• The number of nodes in each linked list is in the range [1, 100].
• 0 <= Node.val <= 9
• It is guaranteed that the list represents a number that does not have leading zeros

My Solution: I solved 2 ways : with recursion without Recursion

package madwani.sushil.leetcode.Jan1_7_2021;

public class AddTwoNumbers {
    static int carryForward = 0;
    static ListNode temp = new ListNode(0);
    static ListNode temp1 = temp;
    public static void main(String[] args) {
        ListNode inp1 = constructInput(new int[] {9,9,9,9,9,9,9});
        ListNode inp2 = constructInput(new int[] {9,9,9,9});
        addTwoNumbersWithRecursion(inp1, inp2); // output 8 -> 9 -> 9 -> 9 -> 0 -> 0 -> 0 -> 1
        addTwoNumbersWithoutRecursion(inp1, inp2);
    }

    public static ListNode addTwoNumbersWithRecursion(ListNode l1, ListNode l2) {
        if (l1 == null && l2 == null) {
            return temp;
        }
        if (l1 == null) {
            while (l2 != null) {
              temp.next = new ListNode(nodeValue(l2.val, 0));
              temp = temp.next;
              l2 = l2.next;
            }
            return temp;
        }
        if (l2 == null) {
            while (l1 != null) {
                temp.next = new ListNode(nodeValue(l1.val, 0));
                temp = temp.next;
                l1 = l1.next;
            }
            return temp;
        }
        temp.next = new ListNode(nodeValue(l2.val, l1.val));
        temp = temp.next;
        addTwoNumbersWithRecursion(l1.next, l2.next);
        if (carryForward != 0) {
            temp.next = new ListNode(carryForward);
            temp = temp.next;
            carryForward = 0;
        }
        return temp1.next;
    }

    public static ListNode addTwoNumbersWithoutRecursion(ListNode l1, ListNode l2) {
        while (l1 != null && l2 != null) {
            temp.next = new ListNode(nodeValue(l2.val, l1.val));
            temp = temp.next;
            l1 = l1.next;
            l2 = l2.next;
        }
        if (l1 != null || l2 != null) {
            if (l1 == null) {
                while (l2 != null) {
                    temp.next = new ListNode(nodeValue(l2.val, 0));
                    temp = temp.next;
                    l2 = l2.next;
                }
            } else  if (l2 == null) {
                while (l1 != null) {
                    temp.next = new ListNode(nodeValue(l1.val, 0));
                    temp = temp.next;
                    l1 = l1.next;
                }
            }
        }
        if (carryForward != 0) {
            temp.next = new ListNode(carryForward);
        }
        return temp1.next;
    }

    public static int nodeValue(int val1, int val2) {
        int val = ( val1 + val2 + carryForward ) % 10;
        carryForward = ( val1 + val2 + carryForward ) / 10;
        return val;
    }

    static ListNode constructInput(int[] ints) {
        if ( ints.length == 0) {
            return null;
        }
        ListNode inp = new ListNode(ints[0]);
        ListNode inp1 = inp;
        for ( int i =1; i< ints.length; i++) {
            inp.next = new ListNode(ints[i]);
            inp = inp.next;
        }
        return inp1;
    }

    static class ListNode {
        int val;
        ListNode next;
        ListNode() {}
        ListNode(int val) { this.val = val; }
        ListNode(int val, ListNode next) {
            this.val = val; this.next = next;
        }
    }
}