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Program to find Fibonacci series results up to nth term in Python
Suppose we have a number n. We have to find the sum of first n Fibonacci terms (Fibonacci sequence up to n terms). If the answer is too large then return result modulo 10^8 + 7.
So, if the input is like n = 8, then the output will be 33 as first few Fibonacci terms are 0 + 1 + 1 + 2 + 3 + 5 + 8 + 13 = 33
To solve this, we will follow these steps −
- m := 10^8+7
- memo := a new map
- Define a function solve() . This will take n, m
- if n is in memo, then
- return memo[n]
- memo[n] := n when n < 2 otherwise (solve(n-1, m) +solve(n-2, m)) mod m
- return memo[n]
- From the main method get the list of memo values and take their sum.
Example
Let us see the following implementation to get better understanding −
m = 10**8+7
memo = {}
def solve(n, m):
if n in memo:
return memo[n]
memo[n] = n if n < 2 else (solve(n-1, m)+solve(n-2, m)) % m
return memo[n]
n = 8
solve(n, m)
print(sum(list(memo.values())[:n]))Input
8
Output
33
Updated on: 12-Oct-2021
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