30秒学会 Dart 片段 – factorial

Calculates the factorial of an integer.

Use recursion.
If n is less than or equal to 1, return 1.
Otherwise, return the product of n and the factorial of n-1.
Throws an exception if n is a negative number.

30秒学会 Python 片段 – min_n

Returns the n minimum elements from the provided list.
If n is greater than or equal to the provided list’s length, then return the original list (sorted in ascending order).

Use sorted() to sort the list,[:n]to get the specified number of elements. Omit the second argument,n`, to get a one-element list.

30秒学会 JavaScript 片段 – sortedLastIndexBy

Returns the highest index at which value should be inserted into array in order to maintain its sort order, based on a provided iterator function.

Check if the array is sorted in descending order (loosely).
Use Array.prototype.map() to apply the iterator function to all elements of the array.
Use Array.prototype.reverse() and Array.prototype.findIndex() to find the appropriate last index where the element should be inserted, based on the provided iterator function.

30秒学会 Golang 片段 – IsOdd

Returns true if the given number is odd, false otherwise.

Checks whether a number is odd or even using the modulo (%) operator.
Returns true if the number is odd, false if the number is even.

30秒学会 Dart 片段 – symmetricDifferenceBy

Returns the symmetric difference between two lists, after applying the provided function to each list element of both.

Use Iterable.toSet() and Iterable.map() to get the unique values in each list after applying fn to them.
Use Iterable.where() in combination with Iterable.contains() to keep only the values in one list and not the other.
Finally, use Iterable.toList() and Iterable.addAll() in combination with the cascade operator (..) to return the result.

30秒学会 PHP 片段 – isPrime

Checks if the provided integer is a prime number.

Check numbers from 2 to the square root of the given number.
Return false if any of them divides the given number, else return true, unless the number is less than 2.

30秒学会 C# 片段 – Fibonacci

Generates an array, containing the Fibonacci sequence, up until the nth term.

Starting with 0 and 1, loop from 2 through n adding the sum of the last two numbers and appending to the sequence.
If n is less or equal to 0, return a list containing 0.