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;
        }
	  //使用栈存储两个链表数据，然后计算
        Stack<ListNode> s1 = new Stack<>();
        Stack<ListNode> s2 = new Stack<>();
        ListNode p = head1, q = head2;
        while (p != null) {
            s1.push(p);
            p = p.next;
        }
        while (q != null) {
            s2.push(q);
            q = q.next;
        }
        int flag = 0;
        if (s1.size() >= s2.size()) {
            p = caculateList(s1, s2);
        } else {
            p = caculateList(s2, s1);
        }
        return p;
    }
  //用于计算，个人感觉代码冗余，却无计可施
    private static ListNode caculateList(Stack<ListNode> s1,Stack<ListNode> s2){
        int flag=0;
        ListNode node=null;
        while (s1.size()>0 && s2.size()>0){
            node=s1.pop();
            node.val=node.val+s2.pop().val+flag;
            flag=node.val/10;
            node.val=node.val%10;
        }
        while (s1.size()>0){
            node=s1.pop();
            node.val=node.val+flag;
            flag=node.val/10;
            node.val=node.val%10;
        }
        if (flag>0){
            ListNode node1=new ListNode(flag);
            node1.next=node;
            node=node1;
        }
        return node;
    }
}