21. 合并两个有序链表 @Python @Go

原题

https://leetcode.cn/problems/merge-two-sorted-lists/

思路

虚拟节点

复杂度

时间：O(n)
空间：O(n)

Python代码

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
        dummy = ListNode(-1)
        curr = dummy
        while list1 or list2:
            if not list1:
                curr.next = list2
                list2 = list2.next
            elif not list2:
                curr.next = list1 
                list1 = list1.next
            elif list1.val <= list2.val:
                curr.next = list1 
                list1 = list1.next
            else:
                curr.next = list2 
                list2 = list2.next
            curr = curr.next 
        return dummy.next
        

Go代码

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func mergeTwoLists(list1 *ListNode, list2 *ListNode) *ListNode {
	dummy := ListNode{}
	cur := &dummy
	for list1 != nil || list2 != nil {
		if list1 == nil {
			cur.Next = list2
			list2 = list2.Next
		} else if list2 == nil {
			cur.Next = list1
			list1 = list1.Next
		} else if list1.Val <= list2.Val {
			cur.Next = list1
			list1 = list1.Next
		} else {
			cur.Next = list2
			list2 = list2.Next
		}
		cur = cur.Next
	}
	return dummy.Next
}