Lecture 38 - Print All Prime From 1 to N

To print all prime numbers from 1 to N, you can modify the previous program to check each number in the range [1, N] for primality. If a number is prime, it will be printed; otherwise, it will be skipped. We can reuse the isPrime function from the previous program to determine whether a number is prime or not.

Here's the C++ program to print all prime numbers from 1 to N:

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#include <iostream> bool isPrime(int number) {    if (number <= 1) {        return false;    }    for (int i = 2; i * i <= number; i++) {        if (number % i == 0) {            return false;        }    }    return true; } int main() {    int N;    std::cout << "Enter a positive integer N: ";    std::cin >> N;    std::cout << "Prime numbers from 1 to " << N << " are: ";    for (int i = 2; i <= N; i++) {        if (isPrime(i)) {            std::cout << i << " ";        }    }    std::cout << std::endl;    return 0; }

Example output:

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Enter a positive integer N: 20 Prime numbers from 1 to 20 are: 2 3 5 7 11 13 17 19

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Enter a positive integer N: 50 Prime numbers from 1 to 50 are: 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47

In this program, we take the input N from the user and then loop through all numbers from 2 to N. For each number, we call the isPrime function to determine if it is prime. If it is prime, we print it on the console.

Feel free to run this program with different values of N to find all the prime numbers within the given range.