Positive Composition Count

Problem

The number of compositions of n into exactly k positive ordered parts is C(n - 1, k - 1) when 1 <= k <= n.

Given n and k, return the count, or 0 when no such composition exists.

Hint

Place k - 1 dividers in the n - 1 gaps between units.

case 1

in: [5,2]

expected: 4

case 2

in: [5,1]

expected: 1

case 3

in: [3,4]

expected: 0

Starter codePython

def positive_composition_count(n, k):
    # Your code here
    pass

3 test cases · run your code against them in the editor