Friday, June 18, 2021
Home coding Write a program to check whether number is prime or not.

# Write a program to check whether number is prime or not.

Given a number and we need to find whether a given number is prime or not.

So what is prime Number?

Prime number is a number that is divisble by itself and 1 .

for example-2,3,5,7,11 …. are prime number because they are divisble by 1 and itself. .

Examples:

``````input:5
output:true

input:7
output:true

input:10
output:false``````

```#include<iostream>
using namespace std;
int main()
{
int num;
cout<<"Enter a number to check Number is prime or not : "<<endl;
cin>>num;
bool flag=0;
for(int i=2;i<=num/2;i++)
{
if(num%i==0)//checking whether number have any other divisor
{
flag =1;//if divisor present then number is not a prime number
break;
}
}
if(flag==0)
{
cout<<num<<" is a prime number"<<endl;
}
else
{
cout<<num<<" is not a prime number"<<endl;
}

}```

Output

```Enter a number to check Number is prime or not : 5
5 is a prime number

```

Expected Time Complexity-O(N) where N is the given number.

Expected space Complexity-O(1).