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) {
        Stack<Integer> s1 = new Stack<>();
        Stack<Integer> s2 = new Stack<>();
        Stack<Integer> s3 = new Stack<>();
        ListNode p1 = head1, p2 = head2;
        while (p1 != null) {
            s1.add(p1.val);
            p1 = p1.next;
        }
        while (p2 != null) {
            s2.add(p2.val);
            p2 = p2.next;
        }
        int m = 0;
        while (!s1.isEmpty() && !s2.isEmpty()) {
            int x = s1.pop();
            int y = s2.pop();
            s3.add((x + y + m) % 10); // 0 0
            m = (x + y + m) / 10;
        }
        while (!s1.isEmpty()) {
            int x = s1.pop();
            s3.add((x + m) % 10);
            m = (x + m) / 10;
        }
        while (!s2.isEmpty()) {
            int x = s2.pop();
            s3.add((x + m) % 10);
            m = (x + m) / 10;
        }
        if(m != 0)s3.add(m);
        ListNode node = new ListNode(s3.pop());
        ListNode head3 = node;
        ListNode cur;
        while(!s3.isEmpty()){
            cur = new ListNode(s3.pop());
            node.next = cur;
            node = cur;
        }
        return head3;
    }
}

三个栈实现链表相加。