LeetCode 精选 TOP 面试题 - Easy series (4)

本篇要开始坚持刷题了，从Leetcode精选面试section开始，本文是easy series题解的记录，会不断更新维护。

104. 二叉树的最大深度

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def maxDepth(self, root: TreeNode) -> int:
        if (root==None): # 递归出口
            return 0
        else:
            l=self.maxDepth(root.left)
            r=self.maxDepth(root.right)
            return max([l,r])+1

234. 回文链表：请判断一个链表是否为回文链表。

时空效率不高的解法：

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

class Solution:
    def isPalindrome(self, head: ListNode) -> bool:
        lst=[]
        if head!=None:
            while head.next!=None:
                lst.append(str(head.val))
                head=head.next
            lst.append(str(head.val))
            flag=True
            for i in range(len(lst)//2):
                if lst[i]!=lst[len(lst)-1-i]:
                    flag=False
            return flag
        else: # [] Null
            return True

优化：

 

237. 删除链表中的节点

请编写一个函数，使其可以删除某个链表中给定的（非末尾）节点。传入函数的唯一参数为 要被删除的节点 。

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

class Solution:
    def deleteNode(self, node):
        """
        :type node: ListNode
        :rtype: void Do not return anything, modify node in-place instead.
        """
        node.val=node.next.val
        node.next=node.next.next

412. Fizz Buzz

class Solution:
    def fizzBuzz(self, n: int) -> List[str]:
        res=[]
        for i in range(1,n+1):
            if i%3==0 and i%5!=0:
                res.append('Fizz')
            elif i%5==0 and i%3!=0:
                res.append('Buzz')
            elif i%5==0 and i%3==0:
                res.append('FizzBuzz')
            else:
                res.append(str(i))
        return res