Algorithms_in_C++  1.0.0
Set of algorithms implemented in C++.
check_prime.cpp File Reference

Reduced all possibilities of a number which cannot be prime. Eg: No even number, except 2 can be a prime number, hence we will increment our loop with i+2 jumping on all odd numbers only. If number is <= 1 or if it is even except 2, break the loop and return false telling number is not prime. More...

#include <cassert>
#include <iostream>
Include dependency graph for check_prime.cpp:

Functions

template<typename T >
bool is_prime (T num)
 
int main ()
 

Detailed Description

Reduced all possibilities of a number which cannot be prime. Eg: No even number, except 2 can be a prime number, hence we will increment our loop with i+2 jumping on all odd numbers only. If number is <= 1 or if it is even except 2, break the loop and return false telling number is not prime.

Copyright 2020

Author
omkarlanghe

A simple program to check if the given number if prime or not.

Function Documentation

◆ is_prime()

template<typename T >
bool is_prime ( num)

Function to check if the given number is prime or not.

Parameters
numnumber to be checked.
Returns
if number is prime, it returns @ true, else it returns @ false.
22  {
23  bool result = true;
24  if (num <= 1) {
25  return 0;
26  } else if (num == 2) {
27  return 1;
28  } else if ((num & 1) == 0) {
29  return 0;
30  }
31  if (num >= 3) {
32  for (T i = 3; (i * i) < (num); i = (i + 2)) {
33  if ((num % i) == 0) {
34  result = false;
35  break;
36  }
37  }
38  }
39  return (result);
40 }

◆ main()

int main ( void  )

Main function

45  {
46  // perform self-test
47  assert(is_prime(50) == false);
48  assert(is_prime(115249) == true);
49 
50  int num;
51  std::cout << "Enter the number to check if it is prime or not" << std::endl;
52  std::cin >> num;
53  bool result = is_prime(num);
54  if (result) {
55  std::cout << num << " is a prime number" << std::endl;
56  } else {
57  std::cout << num << " is not a prime number" << std::endl;
58  }
59 
60  return 0;
61 }
Here is the call graph for this function:
is_prime
bool is_prime(T num)
Definition: check_prime.cpp:22
std::cout
std::endl
T endl(T... args)
std::cin