234. 回文链表--PYTHON

最新推荐文章于 2024-03-05 09:41:27 发布

原创最新推荐文章于 2024-03-05 09:41:27 发布 · 236 阅读

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本文介绍了两种检测链表是否为回文的算法：暴力破解法和反转链表法。暴力破解法通过将链表元素转化为数组并检查其是否为回文来实现；反转链表法则通过将链表后半部分反转并与前半部分比较来判断。文章详细解释了两种方法的实现过程。

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自己1：暴力破解

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

class Solution(object):
    def isPalindrome(self, head):
        """
        :type head: ListNode
        :rtype: bool
        """

        num_list = list()
        p = head
        while p:
            num_list.append(p.val)
            p = p.next
        
        flag = True
        for i in range(len(num_list)/2):
            if num_list[i] != num_list[-(i+1)]:
                flag = False
        
        return flag

自己2：反转链表法

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

class Solution(object):
    def isPalindrome(self, head):
        """
        :type head: ListNode
        :rtype: bool
        """

        if not head or not head.next:
            return True

        slow = head
        fast = head.next
        pre = prepre = None
        while fast and fast.next:

            pre = slow
            slow = slow.next
            fast = fast.next.next

            pre.next = prepre
            print(pre)
            prepre = pre
        
        p2 = slow.next
        slow.next = pre

        if fast:
            p1 = slow
        else:
            p1 = slow.next

        while p1:
            if p1.val != p2.val:
                return False
            p1 = p1.next
            p2 = p2.next
        return True