java/002_Add_Two_Numbers.java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    // example in leetcode book
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
    	ListNode dummyHead = new ListNode(0);
    	ListNode p = l1, q= l2, curr = dummyHead;
    	int carry = 0;
    	while (p != null || q!= null) {
    		int x = (p != null) ? p.val : 0;
    		int y = (q != null) ? q.val : 0;
    		int digit = carry + x + y;
    		carry = digit / 10;
    		curr.next = new ListNode(digit % 10);
    		curr = curr.next;
    		if (p != null) p = p.next;
    		if (q != null) q = q.next;
    	}
    	if (carry > 0) {
    		curr.next = new ListNode(carry);
    	}
    	return dummyHead.next;
    }
}