Detailed explanation of random number function in C++

Detailed explanation of random number function in C

Random number plays an important role in computer programming. It can be used to simulate random events, generate random number sequences, etc. Various applications. The C language provides a series of random number functions to facilitate developers to generate and apply random numbers. This article will introduce in detail the usage and precautions of the random number function in C.

In C, the random number function mainly includes two aspects: pseudo-random number generation function and auxiliary random number function.

First, let’s introduce the pseudo-random number generation function in C. The random number library <random></random> introduced in C 11 provides a more flexible and efficient pseudo-random number generation function. It mainly includes the following important classes:

1. std::random_device: This class is used to generate real random number seeds, which can be operated by a hardware random number generator or The random number interface provided by the system can be obtained.
2. std::seed_seq: This class is used to generate a random number seed sequence. Multiple seed values ​​can be combined together to generate a seed sequence, providing a more complex random number generation method.
3. std::mt19937, std::mt19937_64: These two classes are pseudo-random number engines that use the Mersenne rotation algorithm to generate high-quality pseudo-random numbers. sequence. std::mt19937Use 32-bit integer as status, std::mt19937_64Use 64-bit integer as status.
4. std::uniform_int_distribution, std::uniform_real_distribution: These two classes are uniformly distributed random number distributors. std::uniform_int_distribution is used to generate uniformly distributed integer random numbers, std::uniform_real_distribution is used to generate uniformly distributed real random numbers.

Use these classes to generate pseudo-random numbers. First, we need to generate a true random number seed using std::random_device. Then, use the seed initialization through the pseudo-random number engine std::mt19937 or std::mt19937_64, and then use the distributor std::uniform_int_distribution or std::uniform_real_distribution Generate random numbers.

The following is a sample code that demonstrates how to generate a uniformly distributed integer random number:

#include <iostream>
#include <random>

int main() {
    std::random_device rd;
    std::mt19937 gen(rd());
    std::uniform_int_distribution<> dis(1, 100);

    for (int i = 0; i < 10; ++i) {
        std::cout << dis(gen) << " ";
    }

    return 0;
}

Running the above code will output 10 random integers between 1 and 100.

In addition to the pseudo-random number generation function, C also provides some auxiliary random number functions for more convenient processing of random numbers. These include:

1. std::rand: This function generates a pseudo-random integer between 0 and RAND_MAX, the default is RAND_MAXThe value is 32767. It should be noted that the rand function usually uses std::srand to set the random number seed, but it can only generate relatively low-quality random numbers.
2. std::srand: This function is used to set the seed value of the pseudo-random number generator. Generally speaking, we can use the system time as the seed value to ensure that the random number sequence generated by the program is different each time it is run.
3. std::shuffle: This function is used to randomly shuffle a sequence. It accepts two iterator parameters and rearranges the sequence according to the current pseudo-random number generator.

Auxiliary random number functions usually exist in the form of C-style functions (such as rand and srand), which are simpler and more direct to use. However, the random numbers generated by these functions are of low quality and are not recommended for use in actual development. In contrast, using the random number library provided by C++11 is more flexible and efficient.

To summarize, C provides a series of random number functions, including both pseudo-random number generation functions and auxiliary random number functions. Among them, the pseudo-random number generation function is more flexible and efficient to use, and is recommended for use in actual development. If you need a simpler and more direct way to generate random numbers, consider using the auxiliary random number function. When using any random number function, you need to pay attention to setting an appropriate random number seed to ensure that the generated random number sequence has high quality and independence.

I hope the introduction of this article can help readers better understand and apply the random number function in C. If you want to use random number related functions, it is recommended to use the random number library introduced in C 11 to take full advantage of its flexibility and efficiency.

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