[70] Climbing Stairs

https://leetcode.com/problems/climbing-stairs/description/

• algorithms
• Easy (42.43%)
• Source Code: 70.climbing-stairs.py
• Total Accepted: 384.1K
• Total Submissions: 875.3K
• Testcase Example: '2'

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

class Solution(object):
    def climbStairs(self, n):
        """
        :type n: int
        :rtype: int
        """
        a, b = 1, 1
        for i in range(1, n):
            a, b = b, a+b
        return b