fib Python

# -*- coding: utf-8 -*-


# 1.递归法
def fib_recur(n):
    assert n >= 0
    if n in (1, 0):
        return n
    return fib_recur(n-1) + fib_recur(n-2)


# 2. 递推法
def fib_loop(n):
    a, b = 0, 1
    for _ in range(n):
        a, b = b, a+b
    return a

# 矩阵法
from numpy import matrix
def fib_matr(n):
    return (matrix([[1, 1], [1, 0]]) ** (n - 1) * matrix([[1], [0]]))[0, 0]


if __name__ == '__main__':
    for i in range(20):
        print(fib_matr(i), end=' ')

iterator

class Fib:
    def __init__(self):
        self.prev = 0
        self.curr = 1

    def __iter__(self):
        return self

    def __next__(self):
        value = self.curr
        self.curr += self.prev
        self.prev = value
        return value


if __name__ == '__main__':
    from itertools import islice
    f = Fib()
    print(list(islice(f,0,10)))

generator

def fib():
    prev, curr = 0, 1
    while True:
        yield curr
        prev, curr = curr, curr + prev

def main():
    f = fib()
    # for _ in range(10):
    #     print(next(f))
    from itertools import islice
    print(list(islice(f, 0, 10)))


if __name__ == '__main__':
    import cProfile
    cProfile.run('main()')