Question

我正在尝试制作一个停止在给定数量的斐波纳契数字生成器，但它通常会超过该数量。我做错了什么？

#Fibonacci number generator
a=0
b=1
print("Fibonacci number generator.")
stopNumber=input("How high do you want to go? If you want to go forever, put n.")
print(1)
while stopNumber=="n":
        a=a+b
        b=b+a
        print(a)
        print(b)
else:
    while int(stopNumber) > a or int(stopNumber) > b:
        a=a+b
        b=b+a
        print(a)
        print(b)

Answer 1

您获得更高价值的原因是因为您在单个循环中拥有a = a+b和b = b+a。因此，当您检查while int(stopNumber) > a or int(stopNumber) > b:中的值时，您会获得True并输入循环，但a = a+b和b = b+a可以生成a和{{1}的值大于b并且由于您在不检查的情况下打印它，因此您获得了更高的值。你应该在循环中只增加一次，如果你在while循环之后编写print语句，你将得不到正确的值

stopNumber

注意：如果输入为prev = 0 curr = 1 print("Fibonacci number generator.") stopNumber = input("How high do you want to go? If you want to go forever, put n.") if stopNumber == 'n': print(curr) curr = prev + curr prev = curr else: while curr<stopNumber: print(curr) curr = prev + curr prev = curr，则代码将永久运行。

Answer 2

同样的，工作和使用一些更智能的技术：

# returns generator
def fib(stop):
    prev, current = 0, 1
    while current < stop:  # a little hack here - python is ok comparing ints to floats
        yield current
        # multiple assginment - operands on the left are "frozen" just before theis instruction
        prev, current = current, prev + current 

# note inf - float('inf') results in "positive infinity" which is an appropriate math concept for "forever"
stop = float(input("How high do you want to go? If you want to go forever, put inf."))

for f in fib(stop):
    print (f)

注意：请不要尝试list(fib(float('inf')))：）

Answer 3

你检查一下stopNumber＆gt; a或b，然后增加a和b，打印它们。如果你只想打印它们是＆lt; = stopNumber而不是像这样：

#Fibonacci number generator
a=0
b=1
print("Fibonacci number generator.")
stopNumber=input("How high do you want to go? If you want to go forever, put n.")
print(1)
while stopNumber=="n":
        a=a+b
        b=b+a
        print(a)
        print(b)
else:
    while True:
        a = a+b
        b = b+a
        if int(stopNumber) >= a:
           print(a)
        if int(stopNumber) >= b:
           print(b)
        else:
          break

Answer 4

使用您的代码：

#Fibonacci number generator
a=0
b=1
print("Fibonacci number generator.")
stopNumber=input("How high do you want to go? If you want to go forever, put n.")
print(1)
while stopNumber=="n" or int(stopNumber) > a+b:
    a, b = b, a+b
    print(b)

Answer 5

第二个＆＃34;而＆＃34;循环始终保持运行＆＃34; a＆＃34;或＆＃34; b＆＃34;低于＆＃34; stopNumber＆＃34;。因此，循环继续运行，直到BOTH＆＃34; a＆＃34;和＆＃34; b＆＃34;大于＆＃34; stopNumber＆＃34;。因此，当＆＃34; b＆＃34;大于＆＃34; stopLimit＆＃34;但是＆＃34; a＆＃34;仍低于＆＃34; stopLimit＆＃34;循环继续运行。因此，第一个应用的修复方法是更改＆＃34;或＆＃34;条件由＆＃34;和＆＃34;之一。

您只是在总和之前检查条件是否适用。然后，在完成总和的那一刻，他们的结果可能大于＆＃34; stopLimit＆＃34 ;;这就是你打印的东西。要解决此问题，您可以添加＆＃34; if＆＃34;用于验证总和结果仍然低于＆＃34; stopNumber＆＃34;。

的声明

以下是这些修补程序的代码：

#Fibonacci number generator
a=0
b=1
print("Fibonacci number generator.")
stopNumber=input("How high do you want to go? If you want to go forever, put n.")
print(1)
while stopNumber=="n":
        a=a+b
        b=b+a
        print(a)
        print(b)
else:
    while int(stopNumber) > a and int(stopNumber) > b:
        a=a+b
        b=b+a
        if int(stopNumber) > a:
            print(a)
        if int(stopNumber) > b:
            print(b)

Answer 6

 #This is a simple yet efficient program using recursion:

def fibonacci_rec(a, b):
    if a >= 0 and b > 0 or a > 0 and b >= 0:
        s = [a, b]
        while a+b <= 1000: #can set any upper boundary  
            f = a+b
            a = b
            b = f
            s.append(f)
            fibonacci_rec(a, b)
        return s
    else:
        return 'Invalid'

print(fibonacci_rec(1, 1))  # You can set any value of a and b, as you like and no need to iterate in here, just call function once and it does the iteration for you!

Answer 7

def fib(n):
    if n == 0:
        return 0
    if n == 1:
        return 1
    return fib(n-1) + fib(n-2)

print("Fibonacci number generator.")
stopNumber=input("How high do you want to go? If you want to go forever, put n.")
if stopNumber == 'n':
    i=1
    while True:
        print 'Fibonacci #{0}: {1}'.format(i, fib(i))
        i=i+1
else:
    for i in range(1,int(n)):
        print 'Fibonacci #{0}: {1}'.format(i, fib(i))

开始Python斐波纳契生成器

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