C++ Program to Display Fibonacci Series

To understand this example, you should have the knowledge of the following C++ programming topics:


The Fibonacci sequence is a series where the next term is the sum of the previous two terms. The first two terms of the Fibonacci sequence is 0 followed by 1.

The Fibonacci sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21

Example 1: Fibonacci Series up to n number of terms

#include <iostream>
using namespace std;

int main() {
    int n, t1 = 0, t2 = 1, nextTerm = 0;

    cout << "Enter the number of terms: ";
    cin >> n;

    cout << "Fibonacci Series: ";

    for (int i = 1; i <= n; ++i) {
        // Prints the first two terms.
        if(i == 1) {
            cout << t1 << ", ";
            continue;
        }
        if(i == 2) {
            cout << t2 << ", ";
            continue;
        }
        nextTerm = t1 + t2;
        t1 = t2;
        t2 = nextTerm;
        
        cout << nextTerm << ", ";
    }
    return 0;
}

Output

Enter the number of terms: 10
Fibonacci Series: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 

Example 2: Program to Generate Fibonacci Sequence Up to a Certain Number

#include <iostream>
using namespace std;

int main() {
    int t1 = 0, t2 = 1, nextTerm = 0, n;

    cout << "Enter a positive number: ";
    cin >> n;

    // displays the first two terms which is always 0 and 1
    cout << "Fibonacci Series: " << t1 << ", " << t2 << ", ";

    nextTerm = t1 + t2;

    while(nextTerm <= n) {
        cout << nextTerm << ", ";
        t1 = t2;
        t2 = nextTerm;
        nextTerm = t1 + t2;
    }
    return 0;
}

Output

Enter a positive integer: 100
Fibonacci Series: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 

Before we wrap up, let's put your understanding of this example to the test! Can you solve the following challenge?

Challenge:

Write a function to find the nth Fibonacci number.

  • Return the nth Fibonacci number where n is a positive integer.
  • The Fibonacci sequence is a series of numbers where a number is found by adding up the two numbers before it. Starting with 0 and 1, the sequence goes: 0, 1, 1, 2, 3, 5, 8, 13, and so on.
  • For example, if n = 6, the return value should be 8.
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