Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.

Given an input string (s) and a pattern (p), implement wildcard pattern matching with support for '?' and '*'.

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'?' Matches any single character.
'*' Matches any sequence of characters (including the empty sequence).

The matching should cover the entire input string (not partial).

Note:

• s could be empty and contains only lowercase letters a-z.
• p could be empty and contains only lowercase letters a-z, and characters like ? or *.

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

Write a SQL query for a report that provides the following information for each person in the Person table, regardless if there is an address for each of those people: FirstName, LastName, City, State

Given an input string (s) and a pattern (p), implement regular expression matching with support for '.' and '*'.

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'.' Matches any single character.
'*' Matches zero or more of the preceding element.

The matching should cover the entire input string (not partial).

Note:

• s could be empty and contains only lowercase letters a-z.
• p could be empty and contains only lowercase letters a-z, and characters like . or *.

The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)

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P   A   H   N
A P L S I I G
Y   I   R

And then read line by line: "PAHNAPLSIIGYIR"

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

最近開始刷 LeetCode，但雖然有些題目解了出來，但還是存在很多似懂非懂的模糊空間，因此想透過記錄的方式記下這些經驗與領略，並用自己的方式表達出來，以釐清這些模糊的空間。

Invert a binary tree.