climbStairs.py

#    -*- coding: utf-8    -*-
'''
You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

Note: Given n will be a positive integer.


Example 1:

Input: 2
Output:  2
Explanation:  There are two ways to climb to the top.

1. 1 step + 1 step
2. 2 steps
Example 2:

Input: 3
Output:  3
Explanation:  There are three ways to climb to the top.

1. 1 step + 1 step + 1 step
2. 1 step + 2 steps
3. 2 steps + 1 step
'''
"""
        :type n: int
        :rtype: int
        """
class Solution:
    def climbStairs(self, n):
        if n == 1:
            return 1
        elif n == 2:
            return 2
        dp = [None]*n
        dp[0] = 1
        dp[1] = 2
        for i in range(2,n):
            dp[i] = dp[i-1] + dp[i-2]
        return dp[-1]

if __name__ == "__main__":
	sol = Solution()
	print(sol.climbStairs(int(raw_input('Enter top height: '))))