题目
The Fibonacci numbers, commonly denoted F(n) form a sequence, called the Fibonacci sequence, such that each number is the sum of the two preceding ones, starting from 0 and 1. That is,
F(0) = 0, F(1) = 1
F(n) = F(n - 1) + F(n - 2), for n > 1.
Given n, calculate F(n).
解题思路
递归或者递推，如果N很大，可以用矩阵倍方的方法
代码
class Solution:
def fib(self, n: int) -> int:
if n == 0:
return 0
if n <= 2:
return 1
f1 = f2 = 1
for i in range(2, n):
f1, f2 = f2, f1 + f2
return f2
