Python describe LeetCode 70. climb stairs

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subject

Suppose you're climbing the stairs . need n You can reach the top of the building .

Every time you climb 1 or 2 A stair . How many different ways can you climb to the top of the building ？

Example 1：

 Input ：n = 2
Output ：2
explain ： There are two ways to climb to the top .
1. 1 rank + 1 rank
2. 2 rank

Example 2：

 Input ：n = 3
Output ：3
explain ： There are three ways to climb to the top .
1. 1 rank + 1 rank + 1 rank
2. 1 rank + 2 rank
3. 2 rank + 1 rank

Tips ：

• 1 <= n <= 45

Python describe

class Solution:
def climbStairs(self, n: int) -> int:
if n == 1:
return 1
if n == 2:
return 2
a,b,n,i = 1,2,n-2,0
while i < n:
a,b = b,a+b
i += 1
return b