sample1.cc 2.4 KB

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  1. // Copyright 2005, Google Inc.
  2. // All rights reserved.
  3. //
  4. // Redistribution and use in source and binary forms, with or without
  5. // modification, are permitted provided that the following conditions are
  6. // met:
  7. //
  8. // * Redistributions of source code must retain the above copyright
  9. // notice, this list of conditions and the following disclaimer.
  10. // * Redistributions in binary form must reproduce the above
  11. // copyright notice, this list of conditions and the following disclaimer
  12. // in the documentation and/or other materials provided with the
  13. // distribution.
  14. // * Neither the name of Google Inc. nor the names of its
  15. // contributors may be used to endorse or promote products derived from
  16. // this software without specific prior written permission.
  17. //
  18. // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  19. // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  20. // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  21. // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  22. // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  23. // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  24. // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25. // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26. // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27. // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  28. // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29. // A sample program demonstrating using Google C++ testing framework.
  30. #include "sample1.h"
  31. // Returns n! (the factorial of n). For negative n, n! is defined to be 1.
  32. int Factorial(int n) {
  33. int result = 1;
  34. for (int i = 1; i <= n; i++) {
  35. result *= i;
  36. }
  37. return result;
  38. }
  39. // Returns true if and only if n is a prime number.
  40. bool IsPrime(int n) {
  41. // Trivial case 1: small numbers
  42. if (n <= 1) return false;
  43. // Trivial case 2: even numbers
  44. if (n % 2 == 0) return n == 2;
  45. // Now, we have that n is odd and n >= 3.
  46. // Try to divide n by every odd number i, starting from 3
  47. for (int i = 3; ; i += 2) {
  48. // We only have to try i up to the square root of n
  49. if (i > n/i) break;
  50. // Now, we have i <= n/i < n.
  51. // If n is divisible by i, n is not prime.
  52. if (n % i == 0) return false;
  53. }
  54. // n has no integer factor in the range (1, n), and thus is prime.
  55. return true;
  56. }