How to write the Fibonacci Sequence?

Question

I had originally coded the program wrongly. Instead of returning the Fibonacci numbers between a range (ie. startNumber 1, endNumber 20 should = only those numbers between 1

Answer 1

Time complexity :

The caching feature reduces the normal way of calculating Fibonacci series from O(2^n) to O(n) by eliminating the repeats in the recursive tree of Fibonacci series :

Code :

import sys

table = [0]*1000

def FastFib(n):
    if n<=1:
        return n
    else:
        if(table[n-1]==0):
            table[n-1] = FastFib(n-1)
        if(table[n-2]==0):
            table[n-2] = FastFib(n-2)
        table[n] = table[n-1] + table[n-2]
        return table[n]

def main():
    print('Enter a number : ')
    num = int(sys.stdin.readline())
    print(FastFib(num))

if __name__=='__main__':
    main()