LeetCode Java First 400 题解-021

Merge Two Sorted Lists    Easy

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

public ListNode mergeTwoLists(ListNode l1, ListNode l2) {

    if (l1 == null)

        return l2;

    if (l2 == null)

        return l1;

    if (l1.val < l2.val) {

        l1.next = mergeTwoLists(l1.next, l2);

        return l1;

    } else {

        l2.next = mergeTwoLists(l1, l2.next);

        return l2;

    }

}

思路：类似归并排序，每次前移一个较小的数字。