C# 0 The Complete Reference

PART I

C h a p t e r   8 :  

A   C l o s e r   L o o k   a t   M e t h o d s   a n d   C l a s s e s  

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PART IPART I

compute the factorial of a number. For comparison purposes, a nonrecursive equivalent 

is also included.

// A simple example of recursion.

using System;

class Factorial {

  // This is a recursive method.

  public int FactR(int n) {

    int result;

    if(n==1) return 1;

    result = FactR(n-1) * n;

    return result;

  }

  // This is an iterative equivalent.

  public int FactI(int n) {

    int t, result;

    result = 1;

    for(t=1; t <= n; t++) result *= t;

    return result;

  }

}

class Recursion {

  static void Main() {

    Factorial f = new Factorial();

    Console.WriteLine("Factorials using recursive method.");

    Console.WriteLine("Factorial of 3 is " + f.FactR(3));

    Console.WriteLine("Factorial of 4 is " + f.FactR(4));

    Console.WriteLine("Factorial of 5 is " + f.FactR(5));

    Console.WriteLine();

    Console.WriteLine("Factorials using iterative method.");

    Console.WriteLine("Factorial of 3 is " + f.FactI(3));

    Console.WriteLine("Factorial of 4 is " + f.FactI(4));

    Console.WriteLine("Factorial of 5 is " + f.FactI(5));

  }

}

The output from this program is shown here:

Factorials using recursive method.

Factorial of 3 is 6

Factorial of 4 is 24

Factorial of 5 is 120

Factorials using iterative method.

Factorial of 3 is 6

Factorial of 4 is 24

Factorial of 5 is 120

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P a r t   I :  

T h e   C #   L a n g u a g e

The operation of the nonrecursive method 

FactI( )

 should be clear. It uses a loop starting 

at 1 and progressively multiplies each number by the moving product.

The operation of the recursive