Program to find Prime Numbers Between given Interval

Given two numbers a and b as interval range, the task is to find the prime numbers in between this interval.

Examples:

Input : a = 1, b = 10
Output : 2, 3, 5, 7

Input : a = 10, b = 20
Output : 11, 13, 17, 19

In the below program, the range of numbers is taken as input and stored in the variables ‘a’ and ‘b’. Then using for-loop, the numbers between the interval of a and b are traversed. For each number in the for loop, it is checked if this number is prime or not. If found prime, print the number. Then the next number in the loop is checked, till all numbers are checked.

Program:

C++

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// C++ program to find the prime numbers
// between a given interval
  
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
    // Declare the variables
    int a, b, i, j, flag;
  
    // Ask user to enter lower value of interval
    cout << "Enter lower bound of the interval: ";
    cin >> a; // Take input
  
    // Ask user to enter upper value of interval
    cout << "\nEnter upper bound of the interval: ";
    cin >> b; // Take input
  
    // Print display message
    cout << "\nPrime numbers between "   
         << a << " and " << b << " are: ";
  
    // Traverse each number in the interval
    // with the help of for loop
    for (i = a; i <= b; i++) 
    {
        // Skip 0 and 1 as they are
        // niether prime nor composite
        if (i == 1 || i == 0)
            continue;
  
        // flag variable to tell
        // if i is prime or not
        flag = 1;
  
        for (j = 2; j <= i / 2; ++j) 
        {
            if (i % j == 0) 
            {
                flag = 0;
                break;
            }
        }
  
        // flag = 1 means i is prime
        // and flag = 0 means i is not prime
        if (flag == 1)
            cout << i << " ";
    }
  
    return 0;
}
  
// This code is contributed by Akanksha Rai

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C

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// C program to find the prime numbers
// between a given interval
  
#include <stdio.h>
  
int main()
{
    // Declare the variables
    int a, b, i, j, flag;
  
    // Ask user to enter lower value of interval
    printf("Enter lower bound of the interval: ");
    scanf("%d", &a); // Take input
  
    // Ask user to enter upper value of interval
    printf("\nEnter upper bound of the interval: ");
    scanf("%d", &b); // Take input
  
    // Print display message
    printf("\nPrime numbers between %d and %d are: ", a, b);
  
    // Traverse each number in the interval
    // with the help of for loop
    for (i = a; i <= b; i++) {
        // Skip 0 and 1 as they are
        // niether prime nor composite
        if (i == 1 || i == 0)
            continue;
  
        // flag variable to tell
        // if i is prime or not
        flag = 1;
  
        for (j = 2; j <= i / 2; ++j) {
            if (i % j == 0) {
                flag = 0;
                break;
            }
        }
  
        // flag = 1 means i is prime
        // and flag = 0 means i is not prime
        if (flag == 1)
            printf("%d ", i);
    }
  
    return 0;
}

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Java

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import java.util.Scanner;
  
// Java program to find the prime numbers
// between a given interval
public class GFG {
  
    // driver code
    public static void main(String[] args)
    {
        Scanner sc = new Scanner(System.in);
        // Declare the variables
        int a, b, i, j, flag;
  
        // Ask user to enter lower value of interval
        System.out.printf("Enter lower bound of the interval: ");
        a = sc.nextInt(); // Take input
  
        // Ask user to enter upper value of interval
        System.out.printf("\nEnter upper bound of the interval: ");
        b = sc.nextInt(); // Take input
  
        // Print display message
        System.out.printf("\nPrime numbers between %d and %d are: ", a, b);
  
        // Traverse each number in the interval
        // with the help of for loop
        for (i = a; i <= b; i++) {
            // Skip 0 and 1 as they are
            // niether prime nor composite
            if (i == 1 || i == 0)
                continue;
        }
  
        // flag variable to tell
        // if i is prime or not
        flag = 1;
  
        for (j = 2; j <= i / 2; ++j) {
            if (i % j == 0) {
                flag = 0;
                break;
            }
        }
  
        // flag = 1 means i is prime
        // and flag = 0 means i is not prime
        if (flag == 1) {
            System.out.println(i);
        }
    }
}

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Python3

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# Python3 program to find the prime 
# numbers between a given interval
  
if __name__ == '__main__':
      
    # Declare the variables
    a, b, i, j, flag = 0, 0, 0, 0, 0
  
    # Ask user to enter lower value of interval
    print("Enter lower bound of the interval:"
                                      end = "")
    a = int(input()) # Take input
    print(a)
      
    # Ask user to enter upper value of interval
    print("Enter upper bound of the interval:"
                                      end = "")
    b = int(input()) # Take input
    print(b)
      
    # Print display message
    print("Prime numbers between", a, "and"
                        b, "are:", end = "")
  
    # Traverse each number in the interval
    # with the help of for loop
    for i in range(a, b + 1):
  
        # Skip 1 as1 is niether
        # prime nor composite
        if (i == 1):
            continue
  
        # flag variable to tell
        # if i is prime or not
        flag = 1
          
        for j in range(2, i // 2 + 1):
            if (i % j == 0):
                flag = 0
                break
              
        # flag = 1 means i is prime
        # and flag = 0 means i is not prime
        if (flag == 1):
            print(i, end = " ")
              
# This code is contributed 
# by Mohit kumar 29

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Output:

Enter lower bound of the interval: 1
Enter upper bound of the interval: 10
Prime numbers between 1 and 10 are: 2 3 5 7 


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