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
        // 使用两个栈存放数据
        Stack<ListNode> stack1 = new Stack<>();
        Stack<ListNode> stack2 = new Stack<>();
        ListNode tmp1 = head1;
        ListNode tmp2 = head2;
        ListNode dummy = new ListNode(-1);
    
        while (tmp1 != null) {
            stack1.push(tmp1);
            tmp1 = tmp1.next;
        }

        while (tmp2 != null) {
            stack2.push(tmp2);
            tmp2 = tmp2.next;
        }
        // count 进位标志位
        int count = 0;
        int val = 0;
        while (stack1.size() > 0 && stack2.size() > 0) {
            val = stack1.pop().val + stack2.pop().val + count;
            if (val >= 10) {
                val = val % 10;
                count = 1;
            } else {
                count = 0;
            }
            ListNode node = new ListNode(val);
            node.next = dummy.next;
            dummy.next = node;
        }

        while (stack1.size() > 0) {
            val = stack1.pop().val + count;
            if (val >= 10) {
                val = val % 10;
                count = 1;
            } else {
                count = 0;
            }
            ListNode node = new ListNode(val);
            node.next = dummy.next;
            dummy.next = node;
        }

        while (stack2.size() > 0) {
            val = stack2.pop().val + count;
            if (val >= 10) {
                val = val % 10;
                count = 1;
            } else {
                count = 0;
            }
            ListNode node = new ListNode(val);
            node.next = dummy.next;
            dummy.next = node;
        }

        return dummy.next;
    }
}