70. Climbing Stairs

class Solution(object):
    def climbStairs(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n==0 or n==1:
            return 1
        dp=[0]* (n+1)

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

        return dp[n]