Hey there coders!

Ready for another coding interview test problem? Today we have a tough one for you. Let’s see how well you can climb stairs. As always, you can write your answer in any programming language or pseudo-code in a gist on github and share it in the comments below!

Difficulty: Hard

There exists a staircase with N steps, and you can climb up either 1 or 2 steps at a time. Given N, write a function that returns the number of unique ways you can climb the staircase. The order of the steps matters.

For example, if N is 4, then there are 5 unique ways:

  • 1, 1, 1, 1
  • 2, 1, 1
  • 1, 2, 1
  • 1, 1, 2
  • 2, 2

What if, instead of being able to climb 1 or 2 steps at a time, you could climb any number from a set of positive integers X? For example, if X = {1, 3, 5}, you could climb 1, 3, or 5 steps at a time.

Got the answer? Share it below.