Kth Factor

Problem

Return the k-th smallest positive divisor of n, or -1 when n has fewer than k divisors.

Collect divisors up to the square root, then append their partners in descending order to obtain the sorted divisor list. Return the k-th entry or -1.

Hint

Small divisors come in ascending order, their partners in descending order.

Test cases

case 1

in: [12,3]

expected: 3

case 2

in: [7,2]

expected: 7

case 3

in: [4,4]

expected: -1

case 4

in: [1,1]

expected: 1

case 5

in: [1000,3]

expected: 4

Starter codePython

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

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