# Answer to Question #23636 in Java | JSP | JSF for Karl

Question #23636

Create programs that, given a range of integers by its lower and upper limit, construct a list of all prime numbers in that range.

Expert's answer

#include <iostream>

#include <math.h>

using namespace std;

/**

* This functionchecks if the number p is prime.

* It suffices toverify that p is not divisible by numbers from 2 to sqrt(p) */ int is_prime_number(int p) {

// skip numbers0 and 1 that are not primes

if (p<2)

{

returnfalse;

}

// number 2 isprime

if (p==2)return true;

float p_sqr =sqrt(p);

for(int i=2; i<= p_sqr; i++)

{

if ( p % i== 0 )

{

returnfalse;

}

}

return true;

}

int main()

{

int minX, maxX;

// get lowerand upper bounds from the user

cout <<"Enter lower bound for the range: ";

cin >>minX;

cout <<"Enter upper bound for the range: ";

cin >>maxX;

if (minX >maxX)

{

cout<< "Incorrect range. Quitting

";

return 0;

}

if (maxX<2)

{

cout<< "The range [" << minX << "," <<

maxX << "] contains no primes.

";

return 0;

}

// increaseminX to 2 if necessary, since there are no primes < 2

if (minX<2)minX=2;

cout <<"List of primes contained in the range [" << minX <<

"," << maxX << "]:

";

int cnt=0; //counter of primes

for(int i=minX;i<=maxX; i++)

{

if(is_prime_number(i))

{

cout<< i << " ";

cnt++;

}

}

if (cnt==0)

{

cout<< "No primes in this range";

}

cout <<endl;

}

#include <math.h>

using namespace std;

/**

* This functionchecks if the number p is prime.

* It suffices toverify that p is not divisible by numbers from 2 to sqrt(p) */ int is_prime_number(int p) {

// skip numbers0 and 1 that are not primes

if (p<2)

{

returnfalse;

}

// number 2 isprime

if (p==2)return true;

float p_sqr =sqrt(p);

for(int i=2; i<= p_sqr; i++)

{

if ( p % i== 0 )

{

returnfalse;

}

}

return true;

}

int main()

{

int minX, maxX;

// get lowerand upper bounds from the user

cout <<"Enter lower bound for the range: ";

cin >>minX;

cout <<"Enter upper bound for the range: ";

cin >>maxX;

if (minX >maxX)

{

cout<< "Incorrect range. Quitting

";

return 0;

}

if (maxX<2)

{

cout<< "The range [" << minX << "," <<

maxX << "] contains no primes.

";

return 0;

}

// increaseminX to 2 if necessary, since there are no primes < 2

if (minX<2)minX=2;

cout <<"List of primes contained in the range [" << minX <<

"," << maxX << "]:

";

int cnt=0; //counter of primes

for(int i=minX;i<=maxX; i++)

{

if(is_prime_number(i))

{

cout<< i << " ";

cnt++;

}

}

if (cnt==0)

{

cout<< "No primes in this range";

}

cout <<endl;

}

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