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。