C# Fibonacci SequenceCompute Fibonacci numbers with an iterative algorithm that uses a for-loop.
Fibonacci. Nature contains many patterns. Fibonacci numbers are a fascinating sequence. This sequence models and predicts financial markets and natural phenomena.
Computational methods. We can compute Fibonacci numbers in C# code with recursion. This approach can be slow. It is also possible to use iteration.
Input and output. To begin, we should review the sequence of numbers itself. When we design our program, we can test against these values.
0, 1, 1, 2, 3, 5, 8, 13...
An example. This is an iterative method. Conceptually, an iterative Fibonacci method stores the result of the previous Fibonacci number before computing the next one.
Note To compute a Fibonacci number at a certain position N, we have to loop through all previous numbers starting at position 0.
Tip If you just want to list Fibonacci numbers, you could change Fibonacci() to simply use Console.WriteLine.
And This would make the method print out each number as it is computed, which would reduce the total amount of computation required.
C# program that computes Fibonacci iteratively
public static int Fibonacci(int n)
int a = 0;
int b = 1;
// In N steps, compute Fibonacci sequence iteratively.for (int i = 0; i < n; i++)
int temp = a;
a = b;
b = temp + b;
static void Main()
for (int i = 0; i < 15; i++)
Problem, overflow. One problem with this implementation is that the int types will overflow past the 47th Fibonacci number. It cannot be used on large numbers.
Tip To solve this problem, you can change Fibonacci() to return double. Also change a, b, and temp to be of type double.