使用动态编程的斐波那契索引超出范围

Question

最近的动态编程引起了我的兴趣。因此，我使用动态编程概念在fibonacci系列上编写了代码，但是每次执行时，我都会遇到数组超出索引范围的情况。我尽力弄清楚了，但无法解决。从错误中，我认为索引在上一次迭代时超出范围。这是我的代码：

def fibo(n) :

# len(mem) being shorter than n will indicate that the position is not filled(memoized)
# if it is equal then is has the required value it wont have to calculate res = fibo(n-1)+ fibo(n-2)
    if len(mem) == n :
        return mem[n]

#General cases
    if n == 1 or n == 2 :
        res = 1
    elif n == 0 :
        res = 0
    else :
        res = fibo(n-1)+ fibo(n-2)

#Here the len(m) should be n-1 and thus we append the value of 'res'so at one point we can return it instead of calculating
    mem.append(res)
    return res

#Start of Program
n = int(input("Enter the position :"))

#Defining mem as a list
mem = []

print(fibo(n))

Answer 1

您需要先在列表中添加1：

mem = [1]
for i in range(1,10):
    print(fibo(i))

1
1
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21
34