C++ program: find first n prime numbers

In this tutorial, we will discuss the concept of an Example C++ Program: find first n prime numbers in C++ language

In this post, we are going to learn how to write a program to find the first n prime number using for, while, and do-while loops in C++ programming language:

Write a program to find first n prime numbers in Java — Prime numbers

The number that can be divided by 1 and itself only. it is called the prime number

for Example 2,3,5,7,11,13, ….

To understand this example program, you should have previous knowledge of the following Java topics

for loop in C language

while loop in C language

do-while loop in C language

if statement in C language

Example program to print first n prime numbers

Print the first n prime number using the for loop

In this program, we will print the first “n” prime numbers, using for loop. First, the user is asked to enter a number randomly for n, and then the program prints the prime numbers 1 to n.

Program 1

//C++ program to find first n prime numbers
#include <iostream>
#include <conio.h>
using namespace std;

int main()
{
    //declare and initialize the variable
    int n,i=3,count1,num;
    cout<<"Enter the count for n to print (0 -n)prime:\n";
    //ask input from the user and store in n
    cin>>n;
  //Generating prime numbers
    if(n>=1){
        cout<<"The First "<<n<<" prime numbers are: \n";
        cout<<"2 ";
    }
    for(count1=2; count1<=n; i++){
        for(num=2; num<i; num++){
            if(i%num==0)
                break;
        }
        if(num==i){
            cout<<i<<" ";
            count1++;
        }
    }
    getch();
    return 0;
}

When the above code is executed, it produces the following result

Enter the count for n to print (0 -n)prime:
6
The First 6 prime numbers are
2  3  5  7  11   13

Print the first n prime number using the while loop

In this program, we will print the first “n” prime numbers, using a while loop. first, the user is asked to enter a number randomly for n, and then the program prints the prime numbers 1 to n.

Program 2

//C++ program to find first n prime numbers
#include <iostream>
#include <conio.h>
using namespace std;

int main()
{
    //declare and initialize the variable
    int n,i=3,count1,num;
    cout<<"Enter the count for n to print (0 -n)prime:\n";
    //ask input from the user and store in n
    cin>>n;
  //Generating prime numbers
    if(n>=1){
        cout<<"irst "<<n<<" prime numbers are: \n";
        cout<<"2 ";
    }
    count1=2;
    while(count1<=n){
            num=2;
        while(num<i){
            if(i%num==0)
                break;
    num++;
        }
        if(num==i){
            cout<<i<<" ";
            count1++;
        }
         i++;
    }
    getch();
    return 0;
}

When the above code is executed, it produces the following result

Enter the count for n to print (0 -n)prime:
15
The First 15 prime numbers are
2  3  5  7  11   13  17  19  23  29  31  37  41  43  47

Print the first n prime number using the do-while loop

In this program, we will print the first “n” prime numbers, using a do-while loop. first, the user is asked to enter a number randomly for n, and then the program prints the prime numbers 1 to n.

Program 3

//C++ program to find first n prime numbers
#include <iostream>
#include <conio.h>
using namespace std;

int main()
{
    //declare and initialize the variable
    int n,i=3,count1,num;
    cout<<"Enter the count for n to print (0 -n)prime:\n";
    //ask input from the user and store in n
    cin>>n;
  //Generating prime numbers
    if(n>=1){
        cout<<"irst "<<n<<" prime numbers are: \n";
        cout<<"2 ";
    }
    count1=2;
    do{
            num=2;
       do{
            if(i%num==0)
                break;
    num++;
        } while(num<i);
        if(num==i){
            cout<<i<<" ";
            count1++;
        }
         i++;
    }while(count1<=n);
    getch();
    return 0;
}

When the above code is executed, it produces the following result

Enter the count for n to print (0 -n)prime:

The First 10 prime numbers are

2 3 5 7 11 13 17 19 23 29

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