剑指offer刷题（十九）

合并两个排序的链表

输入两个递增排序的链表，合并这两个链表并使新链表中的节点仍然是递增排序的。

示例1：

输入：1->2->4, 1->3->4
输出：1->1->2->3->4->4
限制：

0 <= 链表长度 <= 1000

解题思路：

java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode p = new ListNode(0);
        ListNode q = p;
        
        while(l1!=null && l2!=null){
            if(l1.val < l2.val){
                q.next = l1;
                l1 = l1.next;
            }
            else{
                q.next = l2;
                l2 = l2.next;
            }
            q = q.next;
        }
        if(l1==null){
            q.next = l2;
        }
        if(l2==null){
            q.next = l1;
        }

        return p.next;
    }
}

python

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def mergeTwoLists(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        p =  ListNode(0)
        q = p
        
        while l1 and l2:
            if l1.val < l2.val:
                q.next = l1
                l1 = l1.next;
            else:
                q.next = l2
                l2 = l2.next
            q = q.next

        if not l1:
            q.next = l2;
        
        if not l2:
            q.next = l1;

        return p.next;