이항 계수 4

65. Valid Number

A valid number can be split up into these components (in order):

1. A decimal number or an integer.
2. (Optional) An ‘e’ or ‘E’, followed by an integer.

A decimal number can be split up into these components (in order):

1. (Optional) A sign character (either ‘+’ or ‘-‘).
2. One of the following formats:

1. One or more digits, followed by a dot ‘.’.
2. One or more digits, followed by a dot ‘.’, followed by one or more digits.
3. A dot ‘.’, followed by one or more digits.

An integer can be split up into these components (in order):

1. (Optional) A sign character (either ‘+’ or ‘-‘).
2. One or more digits.

For example, all the following are valid numbers: [“2”, “0089”, “-0.1”, “+3.14”, “4.”, “-.9”, “2e10”, “-90E3”, “3e+7”, “+6e-1”, “53.5e93”, “-123.456e789”], while the following are not valid numbers: [“abc”, “1a”, “1e”, “e3”, “99e2.5”, “—6”, “-+3”, “95a54e53”].

Given a string s, return true if s is a valid number.

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성대나라의 물탱크

주식회사 승범이네

자동차 공장

트리와 쿼리5

경주

1746. Maximum Subarray Sum After One Operation

You are given an integer array nums. You must perform exactly one operation where you can replace one element nums[i] with nums[i] * nums[i].

Return the maximum possible subarray sum after exactly one operation. The subarray must be non-empty.

99. Recover Binary Search Tree

You are given the root of a binary search tree (BST), where the values of exactly two nodes of the tree were swapped by mistake. Recover the tree without changing its structure.