PROBLEM

ASKED by Amazon.com

There's a staircase with N steps, and you can climb 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. Generalize your function to take in X.

Run with gradlew :

./gradlew run -Psize={STAIR_SIZE} -Psteps={LIST_OF_STEPS }

Where STAIR SIZE is Int and LIST_OF_STEPS is a string composed of int separated by comma.

Example :

./gradlew run -Psize=4 -Psteps=1,2,3