Climb Stairs

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?

Solution

class Solution(object):
    def climbStairs(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n == 1:
            return 1
        elif n == 2:
            return 2

        dp = [0] * n
        dp[0], dp[1] = 1, 2
        for i in range(2, n):
            dp[i] = dp[i-1] + dp[i-2]
        return dp[-1]

public class Solution {
    public int climbStairs(int n) {
        if(n < 3) return n;
        int [] dp  = new int[n + 1];

        dp[1] = 1;
        dp[2] = 2;
        for(int i = 3;i<=n;i++)
            dp[i] = dp[i-1] + dp[i-2];
        return dp[n];
    }
}