Question

2. Write a function to test primality Use the definition of prime number to guide your implementation of the following function. After testing it for correctness, think about how the following result can be used to improve the efficiency. For any positive integers n, r, s, if n=rs, then r<=sqrt(n) or s<=sqrt(n) /* return true if n is prime return false if n is not prime Precondition: n>1 bool IsPrime (int n)

c++

Answer 1

CODE:

#include<iostream>
#include<math.h>
using namespace std;

bool IsPrime(int n){
   int i,flag=0; //flag to check number having factors or not
   for(i=2;i<=sqrt(n);i++) //check each number upto sqrt(n)
       if(n%i==0){ //if number is factor then fkag set 1 and break the loop
           flag=1;
           break;
       }
   if((flag)||(n==1)) //loop was terminated at flag=1 that means not a prime
       return false;
   else              //if flag strill 0 then that was prime number
       return true;
}
int main(){
   int n;
   cout<<"Enter Number: ";
   cin>>n;   //input the number to test primality
   if(IsPrime(n))
       cout<<n<<" is prime"; //printing result
   else
       cout<<n<<" is not a prime";
   return 0;
}

output: