"Angry Professor" Python implementation Problem Statement


  The professor is conducting a course on Discrete Mathematics to a class of N students. He is angry at the lack of their discipline, and he decides to cancel the class if there are fewer than K students present after the class starts.
  
  Given the arrival time of each student, your task is to find out if the class gets cancelled or not.
  
  Input Format
  
  The first line of the input contains T, the number of test cases. Each test case contains two lines. 
  The first line of each test case contains two space-separated integers, N and K. 
  The next line contains N space-separated integers, \$a_1,a_2,…,a_N\$, representing the arrival time of each student.
  
  If the arrival time of a given student is a non-positive integer (\$a_i≤0\$), then the student enters before the class starts. If the arrival time of a given student is a positive integer (\$a_i&gt;0\$), the student enters after the class has started.
  
  Output Format
  
  For each testcase, print "YES" (without quotes) if the class gets cancelled and "NO" (without quotes) otherwise.
  
  Constraints
  
  $$\begin{align}
1&amp;≤T≤10,\\
1&amp;≤N≤1000,\\
1&amp;≤K≤N,\\
−100&amp;≤a_i≤100, \text{where}\ i∈[1,N]
\end{align}$$
  
  Note
  
  If a student enters the class exactly when it starts (\$a_i=0\$), the student is considered to have entered before the class has started.
  
  Sample Input

2
4 3
-1 -3 4 2
4 2
0 -1 2 1

  
  Sample Output

YES
NO



Solution

def is_on_time(a):
    return a &lt;= 0

def class_cancelled(expected, arrival_times):
    actual = map(lambda x: 1 if is_on_time(x) else 0, arrival_times).count(1)
    return actual &gt;= expected

def read_int():
    return int(raw_input())

def read_ints():
    return map(int, raw_input().strip().split())

if __name__ == '__main__':
    T = read_int()
    for _ in xrange(T):
        N, K = read_ints()
        A = read_ints()
        print "NO" if class_cancelled(K, A) else "YES"
def class_cancelled(expected, arrival_times):
    ....
    return actual &gt;= expected

print "NO" if class_cancelled(K, A) else "YES"


class_cancelled is a misnomer. It in fact computes a class_not_cancelled condition: class should be cancelled when actual &lt; expected. Also the problem asks to print "Yes" when the class gets cancelled. Funny how two wrongs make it right.