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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 | ||
30 | // A sample program demonstrating using Google C++ testing framework. | |
31 | // | |
32 | // Author: wan@google.com (Zhanyong Wan) | |
33 | ||
34 | #include "sample1.h" | |
35 | ||
36 | // Returns n! (the factorial of n). For negative n, n! is defined to be 1. | |
37 | int Factorial(int n) { | |
38 | int result = 1; | |
39 | for (int i = 1; i <= n; i++) { | |
40 | result *= i; | |
41 | } | |
42 | ||
43 | return result; | |
44 | } | |
45 | ||
46 | // Returns true iff n is a prime number. | |
47 | bool IsPrime(int n) { | |
48 | // Trivial case 1: small numbers | |
49 | if (n <= 1) return false; | |
50 | ||
51 | // Trivial case 2: even numbers | |
52 | if (n % 2 == 0) return n == 2; | |
53 | ||
54 | // Now, we have that n is odd and n >= 3. | |
55 | ||
56 | // Try to divide n by every odd number i, starting from 3 | |
57 | for (int i = 3; ; i += 2) { | |
58 | // We only have to try i up to the squre root of n | |
59 | if (i > n/i) break; | |
60 | ||
61 | // Now, we have i <= n/i < n. | |
62 | // If n is divisible by i, n is not prime. | |
63 | if (n % i == 0) return false; | |
64 | } | |
65 | ||
66 | // n has no integer factor in the range (1, n), and thus is prime. | |
67 | return true; | |
68 | } |