【leetcode 509】 斐波那契数

动态规划的方法

class Solution:
    def fib(self, N: int) -> int:
        dp = (N+1)*[0]
        if N<1: return 0
        dp[1] = 1
        for i in range(2,N+1):
            dp[i] = dp[i-1] + dp[i-2]
        return dp[N]