Function part 4 (Random functions)

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Random functions in C++ are used to generate random numbers. There are two built-in random functions in C++: rand() and srand().

The rand() function generates a random integer between 0 and RAND_MAX, where RAND_MAX is a macro that is defined in the cstdlib header file. The srand() function is used to seed the random number generator. If you don’t call srand(), the random number generator will be seeded with a default value.

Example 1:

#include <iostream>
#include <cstdlib>

using namespace std;
int main()
{
    
    cout << rand() << endl;
    
    return 0;
}

This code prints a random integer to the console.

Example 2:

#include <iostream>
#include <cstdlib>

using namespace std;
int main()
{
    for (size_t i = 0; i < 10; i++)
    {
        cout << rand() << endl;
    }
    
    return 0;
}

This code is a for loop that prints 10 random integers to the console.

Example 3:

#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
    for (size_t i = 0; i < 10; i++)
    {
        cout << rand()%10 << endl;
    }
    
    return 0;
}

This code generates a random number between 0 and 9 and prints it to the console. The modulus operator (%) returns the remainder of a division operation. So, the expression rand()%10 will return the remainder of the operation rand() / 10. This will give us a number between 0 and 9.

Example 4:

#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
    for (size_t i = 1; i <= 10; i++)
    {
        cout << rand()%(30 - 20 + 1) + 20 << endl;
    }
    
    return 0;
}

This code generates a random number between 20 and 30 and prints it to the console.

Example 5:

#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;

int main()
{
    srand(time(0));
    for (size_t i = 1; i <= 10; i++)
    {
        cout << rand()%(30 - 20 + 1) + 20 << endl;
    }
    
    return 0;
}

The srand(time(0)); function seeds the random number generator with the current time. This ensures that the random numbers are different each time the program is run.

The srand() function takes an integer seed as its argument and initializes the random number generator with that seed. The time(0) function returns the current time as a time_t value, which is an integer.

By seeding the random number generator with the current time, we are using a value that is constantly changing, which ensures that the random numbers are different each time the program is run.

It is important to seed the random number generator before using the rand() function. If you do not seed the random number generator, it will be seeded with a default value, which will result in the same sequence of random numbers being generated each time the program is run.

Example 6:

#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;

int main()
{
    int x, y;
    x = time(0);
    for (size_t i = 0; i < 10000; i++)
    {
        cout << time(NULL) << endl;
        y = time (0);
    }
    cout << "The token time:" << y - x << endl;
    return 0;
}

This code prints the current time 10000 times to the console and then prints the total time it took to do so.

The program works as follows:

  1. The int x, y; declaration creates two integer variables, x and y.
  2. The x = time(0); statement assigns the current time to the variable x.
  3. The for (size_t i = 0; i < 10000; i++) loop iterates 10000 times.
  4. On each iteration of the for loop, the following code is executed:
    • The current time is printed to the console using the cout << time(NULL) << endl; statement.
  5. The y = time(0); statement assigns the current time to the variable y.
  6. The cout << "The token time:" << y - x << endl; statement prints the total time it took to print the current time 10000 times to the console.

The time(NULL) function is a synonym for the time(0) function.

You can use this code to measure the performance of your code or to calculate the elapsed time between two events.

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Function part 4 (Random functions)

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