501. Find Mode in Binary Search Tree查找BST中的众数

[抄题]:

Given a binary search tree (BST) with duplicates, find all the mode(s) (the most frequently occurred element) in the given BST.

Assume a BST is defined as follows:

  • The left subtree of a node contains only nodes with keys less than or equal to the node‘s key.
  • The right subtree of a node contains only nodes with keys greater than or equal to the node‘s key.
  • Both the left and right subtrees must also be binary search trees.

For example:
Given BST [1,null,2,2],

   1
         2
    /
   2

return [2].

[暴力解法]:

时间分析:

空间分析:hashmap:n

[优化后]:

时间分析:

空间分析:各种count

[奇葩输出条件]:

返回具体元素,不是次数。所以反过来 nums[次数] = 元素。

[奇葩corner case]:

[思维问题]:

新建数组指定空间,多大不知道,所以需要提前遍历一下

[一句话思路]:

先存maxcount,符合要求之后再存modecount

[输入量]:空: 正常情况:特大:特小:程序里处理到的特殊情况:异常情况(不合法不合理的输入):

[画图]:

[一刷]:

  1. 有返回值的单个函数中,必须把全局变量再写一遍
  2. 要处理的情况写if, else if,不处理的不用管
  3. inorder遍历本质是dfs,也有退出条件

[二刷]:

[三刷]:

[四刷]:

[五刷]:

[五分钟肉眼debug的结果]:

[总结]:

[复杂度]:Time complexity: O() Space complexity: O()

[英文数据结构或算法,为什么不用别的数据结构或算法]:

[关键模板化代码]:

[其他解法]:

[Follow Up]:

[LC给出的题目变变变]:

[代码风格] :

原文地址:https://www.cnblogs.com/immiao0319/p/8973041.html

时间: 2024-11-05 21:55:01

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