两数相加——力扣

执行用时：

1 ms, 在所有 Java 提交中击败了100.00% 的用户

内存消耗：

41.3 MB, 在所有 Java 提交中击败了76.16% 的用户

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        int addNumber = 0;
        ListNode l3 = null;
        int s = 0;
        do {
            int a = 0,b=0;
            if (l1 != null) {
                a = l1.val;
                l1 = l1.next;
            }
            if (l2 != null) {
                b = l2.val;
                l2 = l2.next;
            }
            if (0 == s) {
                l3 = new ListNode((a + b) % 10);
                addNumber = (a + b)>=10 ? 1 : 0;
            }else {
                add(l3, new ListNode((a + b + + addNumber) % 10));
                addNumber = (a + b + addNumber)>=10 ? 1 : 0;
            }
            s++;
        } while (l1 != null || l2 != null);
        if (addNumber == 1) {
            add(l3, new ListNode(1));
        }
        return l3;
    }

    public static void add(ListNode node, ListNode addNode) {
        if (node.next == null) {
            node.next = addNode;
        }else {
            add(node.next, addNode);
        }
    }
}
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