[LeetCode] [DP] 70. Climbing Stairs

You are climbing a staircase. It takes n steps to reach the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

 

Example 1:

Input: n = 2

Output: 2

Explanation: There are two ways to climb to the top. 1. 1 step + 1 step 2. 2 steps

 

Example 2:

Input: n = 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

 

Constraints:

• 1 <= n <= 45

class Solution:
    def climbStairs(self, n: int) -> int:
        if n ==1:
            return 1
        elif n ==2:
            return 2

        dp = [0 for _ in range(n+2)]
        dp[1] = 1
        dp[2] = 2
        
        for i in range(3,n+1):
            #print(i)
            dp[i] = dp[i-1] + dp[i-2]

        return dp[n]

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