第n个斐波那契数

Question

我未能仅打印第n个斐波纳契数。在我的代码中，当用户说打印第nth trem时，它会打印到第n项的序列，但我只想获得第n项的输出，例如，如果我说num=4，输出应该是2

请指导

代码如下:

N= int(input("How many terms? "))


N1 = 0
N2 = 1
sum = 2


if N <= 0:
   print("Plese enter a positive integer")
elif N == 1:
   print("Fibonacci sequence:")
   print(N1)
else:
   print("Fibonacci sequence:")
   print(N1,",",N2,end=' , ')
   while sum < N:
       Nth = N1 + N2
       print(Nth,end=' , ')

       N1 = N2
       N2 = Nth
       sum += 1

Answer 1

要实现该输出，您可以简单地将 n 的值减少 1，然后继续进行所有计算。例如：

def fib(n):
    n = n-1
    a, b = 0, 1
    count = 1
    while count <= abs(n):
        next = a + b
        a = b
        b = next
        count += 1
    return a 

Answer 2

更简单的代码，来自“如何像计算机科学家一样思考：Python”一书，

def fibonacci (n):
    if n == 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fibonacci(n-1) + fibonacci(n-2)

只需将斐波那契通过您的第 n 项作为参数。

Answer 3

打印语句应在循环之外

N= int(input("How many terms? "))


N1 = 0
N2 = 1
sum = 2


if N <= 0:
   print("Plese enter a positive integer")
elif N == 1:
   print("Fibonacci sequence:")
   print(N1)
else:
   print("Fibonacci sequence:")
   print(N1,",",N2,end=' , ')
   while sum < N:
       Nth = N1 + N2

       N1 = N2
       N2 = Nth
       sum += 1
   print(Nth,end=' , ')