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 // Copyright 2005, Google Inc.

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 //

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 // modification, are permitted provided that the following conditions are

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 //

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 //     * Neither the name of Google Inc. nor the names of its

 // contributors may be used to endorse or promote products derived from

 // this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

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 // A sample program demonstrating using Google C++ testing framework.

 //

 // Author: wan@google.com (Zhanyong Wan)

 #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;

 }