﻿ C# Sharp Exercises: Check a number is prime number or not - w3resource

# C# Sharp Exercises: Check a number is prime number or not

## C# Sharp Recursion : Exercise-7 with Solution

Write a program in C# Sharp to check whether a number is prime or not using recursion.

Sample Solution:-

C# Sharp Code:

``````using System;

class RecExercise7
{
public static int Main()
{
int n1,primeNo;

Console.WriteLine("\n\n Recursion : Check a number is prime number or not :");
Console.WriteLine("--------------------------------------------------------");

Console.Write(" Input any positive number : ");

primeNo = checkForPrime(n1,n1/2);//call the function checkForPrime

if(primeNo==1)
Console.Write(" The number {0} is a prime number. \n\n",n1);
else
Console.WriteLine(" The number {0} is not a prime number. \n\n",n1);
return 0;
}

static int checkForPrime(int n1,int i)
{
if(i==1)
{
return 1;
}
else
{
if(n1 %i==0)
return 0;
else
return checkForPrime(n1,i-1);//calling the function checkForPrime itself recursively
}
}
}
```
```

Sample Output:

```Recursion : Check a number is prime number or not :
--------------------------------------------------------
Input any positive number : 5
The number 5 is a prime number.
```

C# Sharp Code Editor:

```using System;

class RecExercise7
{
public static int Main()
{
int n1,primeNo;

Console.WriteLine("\n\n Recursion : Check a number is prime number or not :");
Console.WriteLine("--------------------------------------------------------");

Console.Write(" Input any positive number : ");

primeNo = checkForPrime(n1,n1/2);//call the function checkForPrime

if(primeNo==1)
Console.Write(" The number {0} is a prime number. \n\n",n1);
else
Console.WriteLine(" The number {0} is not a prime number. \n\n",n1);
return 0;
}

static int checkForPrime(int n1,int i)
{
if(i==1)
{
return 1;
}
else
{
if(n1 %i==0)
return 0;
else
return checkForPrime(n1,i-1);//calling the function checkForPrime itself recursively
}
}
}```

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