leadecode 2 Add Two Numbers

package leadcode;

/**
 * 2. Add Two Numbers
 * Medium
 * 4067
 * 953
 *
 *
 * 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 contain a single digit.
 * Add the two numbers and return it as a linked list.
 *
 * You may assume the two numbers do not contain any leading zero, except the number 0 itself.
 *
 * Example:
 *
 * Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
 * Output: 7 -> 0 -> 8
 * Explanation: 342 + 465 = 807.
 */


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }

class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

    }
}
 */
public class L2 {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode head = new ListNode(0);
        ListNode cur = head;
        int carry = 0;
        while (l1!=null || l2!=null){
            int x = (l1!=null)?l1.val:0;
            int y = (l2!=null)?l2.val:0;
            int sum = x+y+carry;
            carry = sum/10;
            cur.next = new ListNode(sum%10);
            cur = cur.next;
            if(l1!=null){
                l1=l1.next;
            }
            if(l2!=null){
                l2=l2.next;
            }
        }
        if(carry!=0){
            cur.next=new ListNode(carry);
        }
        return head.next;
    }
    

    public static int[] stringToIntegerArray(String input) {
        input = input.trim();
        input = input.substring(1, input.length() - 1);
        if (input.length() == 0) {
            return new int[0];
        }

        String[] parts = input.split(",");
        int[] output = new int[parts.length];
        for(int index = 0; index < parts.length; index++) {
            String part = parts[index].trim();
            output[index] = Integer.parseInt(part);
        }
        return output;
    }

    public static ListNode stringToListNode(String input) {
        // Generate array from the input
        int[] nodeValues = stringToIntegerArray(input);

        // Now convert that list into linked list
        ListNode dummyRoot = new ListNode(0);
        ListNode ptr = dummyRoot;
        for(int item : nodeValues) {
            ptr.next = new ListNode(item);
            ptr = ptr.next;
        }
        return dummyRoot.next;
    }

    public static String listNodeToString(ListNode node) {
        if (node == null) {
            return "[]";
        }

        String result = "";
        while (node != null) {
            result += Integer.toString(node.val) + ", ";
            node = node.next;
        }
        return "[" + result.substring(0, result.length() - 2) + "]";
    }

    public static void main(String[] args) throws IOException {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String line;
        while ((line = in.readLine()) != null) {
            ListNode l1 = stringToListNode(line);
            line = in.readLine();
            ListNode l2 = stringToListNode(line);

            ListNode ret = new L2().addTwoNumbers(l1, l2);

            String out = listNodeToString(ret);

            System.out.print(out);
        }
    }
}

class ListNode {
    int val;
    ListNode next;
    ListNode(int x) {
        val = x;
    }
}