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
        List<ListNode> nodeList1 = new ArrayList<>();
        if (head1 != null) {
            nodeList1.add(head1);
            ListNode temp = head1;
            while (true) {
                ListNode next = temp.next;
                if (next == null) break;
                nodeList1.add(next);
                temp = next;
            }
        }

        List<ListNode> nodeList2 = new ArrayList<>();
        if (head2 != null) {
            nodeList2.add(head2);
            ListNode temp = head2;
            while (true) {
                ListNode next = temp.next;
                if (next == null) break;
                nodeList2.add(next);
                temp = next;
            }
        }

        List<ListNode> loopList1 = new ArrayList<>();
        List<ListNode> loopList2 = new ArrayList<>();
        int loopNum = Math.max(nodeList1.size(), nodeList2.size());
        if (nodeList1.size() > nodeList2.size()) {
            loopList1.addAll(nodeList1);
            loopList2.addAll(nodeList2);
        } else {
            loopList1.addAll(nodeList2);
            loopList2.addAll(nodeList1);
        }

        ListNode next = null;
        int count = 0;
        for (int i = 1; i <= loopNum; i++) {
            ListNode temp1 = loopList1.get(loopList1.size() - i);
            int val1 = temp1.val;
            int targetVal = 0;
            int sum = 0;
            if (loopList2.size() - i < 0) {
                sum = val1 + count;
            } else {
                ListNode temp2 = loopList2.get(loopList2.size() - i);
                int val2 = temp2.val;
                sum = val1 + val2 + count;
            }
            if (sum < 10) {
                count = 0;
                targetVal = sum;
            } else {
                count = 1;
                targetVal = sum - 10;
            }
            ListNode target = new ListNode(targetVal);
            target.next = next;
            next = target;
        }

        if(count == 1){
            ListNode target = new ListNode(1);
            target.next = next;
            next = target;
        }

        return next;
    }
}