链表求和 Ⅱ

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;      
 *     }          
 * }
 */
public class Solution {
    /**
     * @param l1: the first list
     * @param l2: the second list
     * @return: the sum list of l1 and l2 
     */
    
    public ListNode addLists2(ListNode l1, ListNode l2) {
        if (l1 == null && l2 == null) {
            return null;
        }
        
        Stack<Integer> stack1 = reverseNode(l1);  
        Stack<Integer> stack2 = reverseNode(l2);  

        ListNode point = new ListNode(0);
        int carry = 0;
        
        while (!stack1.isEmpty() && !stack2.isEmpty()) {
            int val = stack1.pop() + stack2.pop() + carry;
            carry = val / 10;
            val = val % 10;
            ListNode temp = new ListNode(val);
            temp.next = point.next;
            point.next = temp;
        }
        
        while (!stack1.isEmpty()) {
            int val = stack1.pop() + carry;
            carry = val / 10;
            val = val % 10;
            ListNode temp = new ListNode(val);
            temp.next = point.next;
            point.next = temp;
        }
        
        while (!stack2.isEmpty()) {
            int val = stack2.pop() + carry;
            carry = val / 10;
            val = val % 10;
            ListNode temp = new ListNode(val);
            temp.next = point.next;
            point.next = temp;
        }
        
        if (carry == 1) {
            ListNode temp = new ListNode(1);
            temp.next = point.next;
            point.next = temp;
        }
        
        return point.next;
    } 
    
    public Stack<Integer> reverseNode(ListNode temp){  
        Stack<Integer> record = new Stack<Integer>();  
        while(temp != null){  
            record.push(temp.val);  
            temp = temp.next;  
        }  
        return record;  
    } 
    
}