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
        if(head1 == null) return head2;
        if (head2 == null)  return head1;
        Stack<ListNode> stack1 = new Stack<>();
        Stack<ListNode> stack2 = new Stack<>();
        ListNode p1 = head1;
        ListNode p2 = head2;
        while(p1 != null){
            stack1.push(p1);
            p1 = p1.next;
        }
        while(p2 != null){
            stack2.push(p2);
            p2 = p2.next;
        }
        int temp = 0;
        ListNode head =new ListNode(-1);
        ListNode nHead = head.next;
        while(!stack1.isEmpty() || !stack2.isEmpty()){
            int val = temp;
            if(!stack1.isEmpty()){
                val +=stack1.pop().val;
            }
            if(!stack2.isEmpty()){
                val+=stack2.pop().val;
            }
            temp = val/10;
            ListNode node = new ListNode(val%10);
            node.next = nHead;
            nHead = node;
        }
        if(temp>0){
            ListNode node = new ListNode(temp);
            node.next = nHead;
            nHead = node;
        }
        return nHead;
    }
}

使用辅助栈 更加简单了代码 使用数组也差不多