g0001_0100.s0024_swap_nodes_in_pairs.Solution.py Maven / Gradle / Ivy

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104 LeetCode algorithm problem solutions

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# #Medium #Top_100_Liked_Questions #Linked_List #Recursion #Data_Structure_II_Day_12_Linked_List
# #Udemy_Linked_List #Big_O_Time_O(n)_Space_O(1)
# #2024_06_04_Time_27_ms_(93.88%)_Space_16.4_MB_(83.92%)

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def swapPairs(self, head: Optional[ListNode]) -> Optional[ListNode]:
        if head is None or head.next is None:  
            return head  
        nxt = head.next

        head.next = self.swapPairs(nxt.next)  
        nxt.next = head

        return nxt