LC 0070 [E] Climbing Stairs - ALawliet/algorithms GitHub Wiki

prereq: Fibonacci Number

---

if we're at stair 5, we could only have come from stair 5-1 = 4 (+1) or stair 5-2 = 3 (+2), so how many ways were there to get to stair 4 and 3?

class Solution:
    @cache
    def climbStairs(self, n: int) -> int: # n >= 1
        if n == 1: return 1 # 1 way to make 1, take a step of 1
        if n == 2: return 2 # 2 ways to make 0, take 2 steps of 1 or take 1 step of 2
        return self.climbStairs(n-1) + self.climbStairs(n-2)

class Solution:
    def climbStairs(self, n: int) -> int:
        if n == 1: return 1
    
        T = [0 for _ in range(n)]
        T[0] = 1
        T[1] = 2
    
        for i in range(2, n):
            T[i] += T[i-1]
            T[i] += T[i-2]
        
        return T[-1]

class Solution:
    def climbStairs(self, n: int) -> int:
        one, two = 1, 1
        
        for _ in range(n - 1):
            temp = one
            one = one + two
            two = temp
            
        return one