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70.py
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70.py
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'''
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
'''
class Solution(object):
def climbStairs(self, n):
"""
:type n: int
:rtype: int
"""
if n == 0:
return 0
dp = [0]*n
dp[0], dp[1] = 1, 2
for index in range(2, n):
dp[index] = dp[index-1] + dp[index-2]
return dp[n-1]
# Time: O(N)
# Space: O(N)