How to print the first ten Fibonacci numbers using C#?

The Fibonacci sequence is a series of numbers where each number is the sum of the two preceding ones, starting from 0 and 1. In C#, we can generate and print the first ten Fibonacci numbers using loops and basic arithmetic operations.

Understanding the Fibonacci Sequence

The Fibonacci sequence begins with 0 and 1. Each subsequent number is calculated by adding the two previous numbers together −

Algorithm

The algorithm follows these steps −

• Initialize the first two Fibonacci numbers: val1 = 0 and val2 = 1

• Print the first two numbers

• Use a loop to calculate and print the remaining numbers by adding the previous two

• Update the variables for the next iteration

Example

using System;
public class Demo {
   public static void Main(string[] args) {
      int val1 = 0, val2 = 1, val3, i, n;

      n = 10;

      Console.WriteLine("First ten Fibonacci numbers:");
      Console.Write(val1 + " " + val2 + " ");

      for(i = 2; i < n; ++i) {
         val3 = val1 + val2;
         Console.Write(val3 + " ");
         val1 = val2;
         val2 = val3;
      }
      Console.WriteLine();
   }
}

The output of the above code is −

First ten Fibonacci numbers:
0 1 1 2 3 5 8 13 21 34

Using Arrays to Store Fibonacci Numbers

An alternative approach uses an array to store all Fibonacci numbers before printing them −

using System;
public class FibonacciArray {
   public static void Main(string[] args) {
      int n = 10;
      int[] fib = new int[n];
      
      fib[0] = 0;
      fib[1] = 1;
      
      for(int i = 2; i < n; i++) {
         fib[i] = fib[i-1] + fib[i-2];
      }
      
      Console.WriteLine("First ten Fibonacci numbers using array:");
      for(int i = 0; i < n; i++) {
         Console.Write(fib[i] + " ");
      }
      Console.WriteLine();
   }
}

The output of the above code is −

First ten Fibonacci numbers using array:
0 1 1 2 3 5 8 13 21 34

Using Recursion

A recursive approach calculates each Fibonacci number by calling itself −

using System;
public class FibonacciRecursive {
   public static int Fibonacci(int n) {
      if(n <= 1) {
         return n;
      }
      return Fibonacci(n-1) + Fibonacci(n-2);
   }
   
   public static void Main(string[] args) {
      Console.WriteLine("First ten Fibonacci numbers using recursion:");
      for(int i = 0; i < 10; i++) {
         Console.Write(Fibonacci(i) + " ");
      }
      Console.WriteLine();
   }
}

The output of the above code is −

First ten Fibonacci numbers using recursion:
0 1 1 2 3 5 8 13 21 34

Comparison of Approaches

Conclusion

The iterative approach using a loop is the most efficient method for generating Fibonacci numbers in C#. It uses constant space and linear time complexity, making it suitable for both small and large sequences without the performance overhead of recursion.