Merge Two Sorted Lists

题目

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.

方法

有序链表，合并成一个有序链表。

   public ListNode mergeTwoLists(ListNode l1, ListNode l2) {        if (l1 == null) {            return l2;        }        if (l2 == null) {            return l1;        }                ListNode head = null;        ListNode end = null;        ListNode first = l1;        ListNode second = l2;        while (first != null && second != null) {            int temp1 = first.val;            int temp2 = second.val;            if (temp1 <= temp2) {                if (head == null) {                    head = first;                     end = head;                } else {                    end.next = first;                    end = first;                }                first = first.next;            } else {                if (head == null) {                    head = second;                     end = head;                } else {                    end.next = second;                    end = second;                }                second = second.next;            }                    }        if (first != null) {            end.next = first;        }        if (second != null) {            end.next = second;        }        return head;    }