题解 | #链表相加(二)#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     *
     * @param head1 ListNode类
     * @param head2 ListNode类
     * @return ListNode类
     */
    public ListNode addInList (ListNode head1, ListNode head2) {
        ArrayList<ListNode> list1 = new ArrayList<>();
        ArrayList<ListNode> list2 = new ArrayList<>();
        ListNode res = new ListNode(0);
        while (head1 != null) {
            ListNode node = new ListNode(head1.val);
            list1.add(node);
            head1 = head1.next;
        }
        while (head2 != null) {
            ListNode node = new ListNode(head2.val);
            list2.add(node);
            head2 = head2.next;
        }
        int k = Math.max(list1.size(), list2.size());
        int carry = 0;
        int size1 = list1.size() - 1;
        int size2 = list2.size() - 1;
        int a=0,b=0;
        while (k>=0) {
            if (size1 < 0) a = 0;
            else a = list1.get(size1).val;
            if (size2 < 0) b = 0;
            else b = list2.get(size2).val;
            ListNode node = new ListNode(0);
            node.val = (a + b + carry) % 10;
            carry = (a + b + carry) / 10;
            ListNode next = res.next;
            res.next = node;
            node.next = next;
            size1--;
            size2--;
            k--;
        }
        if (carry > 0) {
            ListNode node = new ListNode(carry);
            ListNode next = res.next;
            res.next = node;
            node.next = next;
            if(res.next.val == 0) res = res.next;
            return res.next;
        }
        if(res.next.val==0) res = res.next;
        return res.next;
    }
}