Using system functions to generate random numbers

The rand () function produces a random number of 0 to Rand_max (32767), with unsigned int double byte is 65535, and four bytes is an integer range of 4294967295.

0~rand_max the probability of each number being selected is the same. The RAND function is internally implemented using linear congruence, which is not a true random number because the periodic

Don't be long, so it can be seen as random.  When the user does not set a random seed, the system default random seed is 1. Rand generates pseudo-random numbers, each time it is executed as a phase

The same, if you want to use random seed function Srand initialization, if the program generates random numbers continuously, it is possible to use srand or there will be a lot of phase

With random numbers, even if the direct use time ((unsigned) times (NULL)) is not resolved as a random seed, it is possible to set the time as a random seed merged

The random number is then used as a random seed for the next generation of random numbers. The complete code used below is available.

static int seed = (unsigned) time (NULL);
int randomonenum (int min,int max,bool bnegative)//Generate a random number
{
if (min <= 0 | | Max < 0 | | min >= max)
{
return 0;
}
Srand (seed);
Seed = rand ();

int num = rand ()% (max+1-min) + min;
if (!bnegative)
{
return num;
}
Return-num;
}

int* randomnums (int min,int max,int n,bool bnegative)//Generate random numbers within the specified range, can have duplicates, can choose to produce negative numbers, positive negative numbers do only one range
{
if (min <= 0 | | Max < 0 | | min >= Max | | n < 0)
{
return NULL;
}

int *pnums = new Int[n];
if (NULL = = pnums)
{
return NULL;
}

for (int i = 0; i < n;i++)
{
Pnums[i] = Randomonenum (min,max,bnegative);
}

return pnums;
}

int* randomnodumpnums (int min,int max,int n,bool bnegative)//generates random numbers within a specified range, cannot be duplicated, can choose to produce negative numbers, and uses set unique attributes to implement

{
if (min <= 0 | | Max < 0 | | min >= Max | | n < 0)
{
return NULL;
}

int *pnums = new Int[n];
if (NULL = = pnums)
{
return NULL;
}

    std::set<int> set_nums;
    int nIndex = 0;
    while (true)
    {
        if (set_ Nums.size () = = N)
        {
             break;
       }
        std::p air<std::set<int>::iterator,bool> Insert_pair;
        Insert_pair = Set_nums.insert (Randomonenum (min,max,bnegative));
        if (Insert_pair.second = = true)
         {
            pnums[nindex++] = *insert_ Pair.first;
       }
   }
    set_nums.clear ();

return pnums;
}

int* RandomNoDumpNums2 (int min,int max,int n,bool bnegative)//generates random numbers within a specified range, cannot be duplicated, by randomly beating the number of normal ranges to achieve
{
if (min <= 0 | | Max < 0 | | min >= Max | | n < 0)
{
return NULL;
}

int *pnums = new Int[n];
if (NULL = = pnums)
{
return NULL;
}

Srand (seed);
Seed = rand ();

    int *temp = new Int[max+1];
    if (bnegative = = False)
    {
         for (int i = 0; I <= max; i++)
        {
    & nbsp;       Temp[i] = i;
       }
   }
    Else
    {
        for (int i = 0; i <= Max; i++)
        {
             Temp[i] =-I;
       }
   }

for (int i = max; i > min;i--)
{
int t = temp[i];
int s = rand ()% (i-min) + min;
Temp[i] = Temp[s];
Temp[s] = t;
}

for (int i = 0; i < n; i++)
{
Pnums[i] = temp[min++];
}
Delete temp;

return pnums;
}

int* RandomNoDumpNums3 (int min,int max,int n,bool bnegative)//Generate random numbers within a specified range, cannot be duplicated, use flag bits to implement

{
if (min <= 0 | | Max < 0 | | min >= Max | | n < 0)
{
return NULL;
}

int *pnums = new Int[n];
if (NULL = = pnums)
{
return NULL;
}

Srand (seed);
Seed = rand ();

int *temp = new Int[max+1];
if (bnegative = = False)
{
for (int i = 0; I <= max; i++)
{
Temp[i] =-1;
}
}
Else
{
for (int i = 0; I <= max; i++)
{
Temp[i] = 1;
}
}

int m = 0;
if (bnegative = = False)
{
for (int i = 0; i < n; i++)
{
m = rand ()% (max+1-min) + min;
while ( -1! = temp[m]);
Pnums[i] = m;
}
}
Else
{
for (int i = 0; i < n; i++)
{
m = rand ()% (max+1-min) + min;
while ( -1! = temp[m]);
Pnums[i] =-M;
}
}
Delete temp;

return pnums;
}

BOOL Istheredumplcates (int array[],int N)
{
Std::set<int> set_nums;
for (int i = 0; i < n; i++)
{
Set_nums.insert (Array[i]);
}
Return! (n = = Set_nums.size ());
}

Test procedure:

int _tmain (int argc, _tchar* argv[])
{
for (int i = 0; i <; i++)
{
int *p = Randomnums (1,15,15);
int *q = Randomnodumpnums (1,15,15);
int *q = RANDOMNODUMPNUMS2 (1,15,15);
int *q = RANDOMNODUMPNUMS2 (1,15,15);
if (NULL! = p)
//         {
for (int m = 0; m < 15;m++)
//             {
cout<<p[m]<< "-";
//             }
cout<<endl;
Delete p;
//         }
cout << "----------------------------------------" <<endl;
if (NULL! = q)
{
for (int n = 0; n < 15;n++)
{
cout<<q[n]<< "-";
}
cout<<endl;
if (Istheredumplcates (q,15))
{
cout<< "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!" <<endl;
}
Delete q;
}
cout << "*****************************************" <<endl;
}

System ("pause");
return 0;
}

Using system functions to generate random numbers