题解 | 链表相加(二)

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head1 ListNode类 
     * @param head2 ListNode类 
     * @return ListNode类
     */
    public ListNode addInList (ListNode head1, ListNode head2) {
        // write code here
        Stack <ListNode> stack1 = new Stack<>();
        Stack <ListNode> stack2 = new Stack<>();

        ListNode p = head1;
        ListNode q = head2;
        while(p!=null){
            stack1.push(p);
            p = p.next;
        }
        while(q!=null){
            stack2.push(q);
            q = q.next;
        }
        int carry = 0;
        int val1,val2,value,total;
        ListNode newList = null;
        while(!stack1.isEmpty() || !stack2.isEmpty() || carry!=0 ){
            if (!stack1.isEmpty()){
                val1 = stack1.pop().val;
            }else{
                val1 = 0;
            }
             if (!stack2.isEmpty()){
                val2 = stack2.pop().val;
            }else{
                val2 = 0;
            }
            total = carry + val1 + val2;
            carry = total / 10;
            value = total % 10;
            ListNode node = new ListNode(value);
            node.next = newList;
            newList = node;
        }


        return newList;

    }
}

纯用栈实现