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596 Classes More Than 5 Students

1. Description Table: Courses +-------------+---------+ | Column Name | Type | +-------------+---------+ | student | varchar | | class | varchar | +-------------+---------+ (student, class) is the primary key column for this table. Each row of this table indicates the name of a student and the class in which they are enrolled. Write an SQL query to report all the classes that have at least five ..

595 Big Countries

1. Description Table: World +-------------+---------+ | Column Name | Type | +-------------+---------+ | name | varchar | | continent | varchar | | area | int | | population | int | | gdp | int | +-------------+---------+ name is the primary key column for this table. Each row of this table gives information about the name of a country, the continent to which it belongs, its area, the population..

594 Longest Harmonious Subsequence

1. Description We define a harmonious array as an array where the difference between its maximum value and its minimum value is exactly 1. Given an integer aray nums, return the length of its longest harmonious subsequence among all its possible subsequences. A subsequence of array is a sequence that can be derived from the array by deleting some or no elements without changing the order of the ..

590 N-ary Tree Postorder Traversal

1. Description Given the root of an n-ary tree, return the postorder traversal of its nodes' values. Nary-Tree input serialization is represented in their level order traversal. Each group of children is separated by the null value. constraints : The number of nodes in the tree is in the range [0, \(10^{4}\)]. 0