1
#include <iostream>
2#include <time.h>
3
4using namespace std;
5
6// generate random numbers
7class randomNumber
8
{
9
public:
10 // initialize the random number generator
11 randomNumber(long s = 0);
12
13 // return a 32-bit random integer m, 1 <= m <= 2^31-2
14 long random();
15
16 // return a 32-bit random integer m, 0 <= m <= n-1,
17 // where n <= 2^31-1
18 long random(long n);
19
20 // return a real number x, 0 <= x < 1
21 double frandom();
22
23private:
24 static const long A;
25 static const long M;
26 static const long Q;
27 static const long R;
28
29 long seed;
30
};
31
32const long randomNumber::A = 48271;
33const long randomNumber::M = 2147483647;
34const long randomNumber::Q = M / A;
35const long randomNumber::R = M % A;
36
37randomNumber::randomNumber(long s)
38{
39 if (s < 0)
40 s = 0;
41
42 if (s == 0)
43
{
44 // get time of day in seconds since 12:00 AM,
45 // January 1, 1970
46 long t_time = time(NULL);
47
48 // mix-up bits by squaring
49 t_time *= t_time;
50 // result can overflow. handle cases
51 // > 0, < 0, = 0
52 if (t_time > 0)
53 s = t_time ^ 0x5EECE66DL;
54 else if (t_time < 0)
55 s = (t_time & 0x7fffffff) ^ 0x5EECE66DL;
56 else
57 s = 0x5EECE66DL;
58
}
59
60 seed = s;
61}
62
63long randomNumber::random()
64{
65 long tmpSeed = A * ( seed % Q ) - R * ( seed / Q );
66
67 if( tmpSeed >= 0 )
68 seed = tmpSeed;
69 else
70 seed = tmpSeed + M;
71
72 return seed;
73}
74
75long randomNumber::random(long n)
76{
77 double fraction = double(random())/double(M);
78
79 return int(fraction * n);
80}
81
82double randomNumber::frandom()
83{
84 return double(random())/double(M);
85}
86