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docs, test: Fit Sieve of Eratosthenes to contributing guidelines (#2803)

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* Update sieve_of_eratosthenes.cpp

* Update doc

---------

Co-authored-by: realstealthninja <68815218+realstealthninja@users.noreply.github.com>
This commit is contained in:
Ritobroto Kalita
2024-10-29 22:38:49 +05:30
committed by GitHub
parent db3f9d3406
commit 649a145234
1 changed files with 72 additions and 22 deletions
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94
math/sieve_of_eratosthenes.cpp
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@@ -1,6 +1,7 @@
/**
* @file
* @brief Get list of prime numbers using Sieve of Eratosthenes
* @brief Prime Numbers using [Sieve of
* Eratosthenes](https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes)
* @details
* Sieve of Eratosthenes is an algorithm that finds all the primes
* between 2 and N.
@@ -11,21 +12,39 @@
* @see primes_up_to_billion.cpp prime_numbers.cpp
*/
#include <cassert>
#include <iostream>
#include <vector>
#include <cassert> /// for assert
#include <iostream> /// for IO operations
#include <vector> /// for std::vector
/**
* This is the function that finds the primes and eliminates the multiples.
* @namespace math
* @brief Mathematical algorithms
*/
namespace math {
/**
* @namespace sieve_of_eratosthenes
* @brief Functions for finding Prime Numbers using Sieve of Eratosthenes
*/
namespace sieve_of_eratosthenes {
/**
* @brief Function to sieve out the primes
* @details
* This function finds all the primes between 2 and N using the Sieve of
* Eratosthenes algorithm. It starts by assuming all numbers (except zero and
* one) are prime and then iteratively marks the multiples of each prime as
* non-prime.
*
* Contains a common optimization to start eliminating multiples of
* a prime p starting from p * p since all of the lower multiples
* have been already eliminated.
* @param N number of primes to check
* @return is_prime a vector of `N + 1` booleans identifying if `i`^th number is a prime or not
* @param N number till which primes are to be found
* @return is_prime a vector of `N + 1` booleans identifying if `i`^th number is
* a prime or not
*/
std::vector<bool> sieve(uint32_t N) {
std::vector<bool> is_prime(N + 1, true);
is_prime[0] = is_prime[1] = false;
std::vector<bool> is_prime(N + 1, true); // Initialize all as prime numbers
is_prime[0] = is_prime[1] = false; // 0 and 1 are not prime numbers
for (uint32_t i = 2; i * i <= N; i++) {
if (is_prime[i]) {
for (uint32_t j = i * i; j <= N; j += i) {
@@ -37,9 +56,10 @@ std::vector<bool> sieve(uint32_t N) {
}
/**
* This function prints out the primes to STDOUT
* @param N number of primes to check
* @param is_prime a vector of `N + 1` booleans identifying if `i`^th number is a prime or not
* @brief Function to print the prime numbers
* @param N number till which primes are to be found
* @param is_prime a vector of `N + 1` booleans identifying if `i`^th number is
* a prime or not
*/
void print(uint32_t N, const std::vector<bool> &is_prime) {
for (uint32_t i = 2; i <= N; i++) {
@@ -50,23 +70,53 @@ void print(uint32_t N, const std::vector<bool> &is_prime) {
std::cout << std::endl;
}
} // namespace sieve_of_eratosthenes
} // namespace math
/**
* Test implementations
* @brief Self-test implementations
* @return void
*/
void tests() {
// 0 1 2 3 4 5 6 7 8 9 10
std::vector<bool> ans{false, false, true, true, false, true, false, true, false, false, false};
assert(sieve(10) == ans);
static void tests() {
std::vector<bool> is_prime_1 =
math::sieve_of_eratosthenes::sieve(static_cast<uint32_t>(10));
std::vector<bool> is_prime_2 =
math::sieve_of_eratosthenes::sieve(static_cast<uint32_t>(20));
std::vector<bool> is_prime_3 =
math::sieve_of_eratosthenes::sieve(static_cast<uint32_t>(100));
std::vector<bool> expected_1{false, false, true, true, false, true,
false, true, false, false, false};
assert(is_prime_1 == expected_1);
std::vector<bool> expected_2{false, false, true, true, false, true,
false, true, false, false, false, true,
false, true, false, false, false, true,
false, true, false};
assert(is_prime_2 == expected_2);
std::vector<bool> expected_3{
false, false, true, true, false, true, false, true, false, false,
false, true, false, true, false, false, false, true, false, true,
false, false, false, true, false, false, false, false, false, true,
false, true, false, false, false, false, false, true, false, false,
false, true, false, true, false, false, false, true, false, false,
false, false, false, true, false, false, false, false, false, true,
false, true, false, false, false, false, false, true, false, false,
false, true, false, true, false, false, false, false, false, true,
false, false, false, true, false, false, false, false, false, true,
false, false, false, false, false, false, false, true, false, false,
false};
assert(is_prime_3 == expected_3);
std::cout << "All tests have passed successfully!\n";
}
/**
* Main function
* @brief Main function
* @returns 0 on exit
*/
int main() {
tests();
uint32_t N = 100;
std::vector<bool> is_prime = sieve(N);
print(N, is_prime);
return 0;
}