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#!/usr/bin/env python3
def climb_stairs(n: int) -> int:
"""
LeetCdoe No.70: Climbing Stairs
Distinct ways to climb a n step staircase where
each time you can either climb 1 or 2 steps.
Args:
n: number of steps of staircase
Returns:
Distinct ways to climb a n step staircase
Raises:
AssertionError: n not positive integer
>>> climb_stairs(3)
3
>>> climb_stairs(1)
1
>>> climb_stairs(-7) # doctest: +ELLIPSIS
Traceback (most recent call last):
...
AssertionError: n needs to be positive integer, your input -7
"""
fmt = "n needs to be positive integer, your input {}"
assert isinstance(n, int) and n > 0, fmt.format(n)
if n == 1:
return 1
dp = [0] * (n + 1)
dp[0], dp[1] = (1, 1)
for i in range(2, n + 1):
dp[i] = dp[i - 1] + dp[i - 2]
return dp[n]
if __name__ == "__main__":
import doctest
doctest.testmod()