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;
        head1 = reverse(head1);
        head2 = reverse(head2);
        ListNode head = new ListNode(-1);
        ListNode nHead = head;
        int temp = 0;
        while(head1 != null ||head2 != null){
            int val = temp;
            if(head1 !=null){
                val+=head1.val;
                head1 = head1.next;
            }
            if(head2 != null){
                val +=head2.val;
                head2 = head2.next;
            }
            temp = val/10;
            nHead.next = new ListNode(val%10);
            nHead = nHead.next;
        }
        if(temp>0){
            nHead.next = new ListNode(temp);
        }
        return reverse(head.next);
    }
    ListNode reverse(ListNode head){
        if(head == null) return head;
        ListNode cur = head;
        ListNode node = null;
        while(cur != null){
            ListNode tail = cur.next;
            cur.next = node;
            node = cur;
            cur = tail;
        }
        return node;
    }
}

思路不是很难就是代码有点难写 只需要弄个反转链表函数加上一个简单的进位处理 创建新链表就行了