from google test sample
#ifndef GTEST_SAMPLES_SAMPLE1_H_ #define GTEST_SAMPLES_SAMPLE1_H_ // Returns n! (the factorial of n). For negative n, n! is defined to be 1. int Factorial(int n); // Returns true iff n is a prime number. bool IsPrime(int n); #endif // GTEST_SAMPLES_SAMPLE1_H_
#include "sample1.h" // Returns n! (the factorial of n). For negative n, n! is defined to be 1. int Factorial(int n) { int result = 1; for (int i = 1; i <= n; i++) { result *= i; } return result; } // Returns true iff n is a prime number. bool IsPrime(int n) { // Trivial case 1: small numbers if (n <= 1) return false; // Trivial case 2: even numbers if (n % 2 == 0) return n == 2; // Now, we have that n is odd and n >= 3. // Try to divide n by every odd number i, starting from 3 for (int i = 3; ; i += 2) { // We only have to try i up to the squre root of n if (i > n/i) break; // Now, we have i <= n/i < n. // If n is divisible by i, n is not prime. if (n % i == 0) return false; } // n has no integer factor in the range (1, n), and thus is prime. return true; }