Find the Nth element of the modified Fibonacci series
Last Updated :
13 Sep, 2022
Given two integers A and B which are the first two terms of the series and another integer N. The task is to find the Nth number using Fibonacci rule i.e. fib(i) = fib(i – 1) + fib(i – 2)
Example:
Input: A = 2, B = 3, N = 4
Output: 8
The series will be 2, 3, 5, 8, 13, 21, …
And the 4th element is 8.
Input: A = 5, B = 7, N = 10
Output: 343
Approach: Initialize variable sum = 0 that stores sum of the previous two values. Now, run a loop from i = 2 to N and for each index update value of sum = A + B and A = B, B = sum. Then finally, return the sum which is the required Nth element.
Below is the implementation of the above approach:
C++
#include <iostream>
using namespace std;
int findNthNumber( int A, int B, int N)
{
int sum = 0;
for ( int i = 2; i < N; i++) {
sum = A + B;
A = B;
B = sum;
}
return sum;
}
int main()
{
int A = 5, B = 7, N = 10;
cout << findNthNumber(A, B, N);
return 0;
}
|
Java
import java.util.*;
class GFG
{
static int findNthNumber( int A, int B, int N)
{
int sum = 0 ;
for ( int i = 2 ; i < N; i++)
{
sum = A + B;
A = B;
B = sum;
}
return sum;
}
public static void main(String[] args)
{
int A = 5 , B = 7 , N = 10 ;
System.out.println(findNthNumber(A, B, N));
}
}
|
Python3
def findNthNumber(A, B, N):
sum = 0
for i in range ( 2 , N):
sum = A + B
A = B
B = sum
return sum
if __name__ = = '__main__' :
A = 5
B = 7
N = 10
print (findNthNumber(A, B, N))
|
C#
using System;
class GFG
{
static int findNthNumber( int A, int B, int N)
{
int sum = 0;
for ( int i = 2; i < N; i++)
{
sum = A + B;
A = B;
B = sum;
}
return sum;
}
public static void Main()
{
int A = 5, B = 7, N = 10;
Console.WriteLine(findNthNumber(A, B, N));
}
}
|
Javascript
<script>
function findNthNumber(A , B , N) {
var sum = 0;
for (i = 2; i < N; i++) {
sum = A + B;
A = B;
B = sum;
}
return sum;
}
var A = 5, B = 7, N = 10;
document.write(findNthNumber(A, B, N));
</script>
|
Time Complexity: O(N)
Auxiliary Space: O(1)
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