Here is my one line Python solution! If there are less students that show up on time than the threshold, we return "YES", otherwise there are enough students and we return "NO".

def angryProfessor(k, a):
    return "YES" if len([i for i in a if i <= 0]) < k else "NO"

c# Solution:

public static string angryProfessor(int k, List<int> a)
{
    return a.Count(x=> x <= 0) < k ? "YES" : "NO";
}

someone need to fix the description in this one

java

public static String angryProfessor(int k, List<Integer> a) {
        a.removeIf(n -> (n > 0));
        return a.size() < k ? "YES" : "NO";
}

This question have some issue in its description it got me confused for a while.

First statement:
The first 3 students arrived on. The last 2 were late. The threshold is 3 students, so class will go on. Return YES.
Leter statement:
Complete the angryProfessor function in the editor below. It must return YES if class is cancelled, or NO otherwise.

Follow the second rule if you want to successfully complete the question.