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.

Daily_coding_Problem_12.py

'''
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

'''
'''
Condition: 
---------  
  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.
'''

def climbStairs(n,steps):
    '''
    Input:
    ------
    n(int):target step
    steps(list):steps at a time
    '''
    climb_stairs=[0]*(n+1)
    climb_stairs[0]=1
    for i in steps:
        if i<=n:
            climb_stairs[i]=1
    for i in range(1,n+1):
        for step in steps:
            if step+i <= n:
                climb_stairs[i+step]+=climb_stairs[i]
    return climb_stairs[n]

'''
Input:
n=45
steps=[1,3,5]

Output:
339200673

'''