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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.
Factorial(int n)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.
IsPrime(int n)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 }
69