C隨機號碼示例

使用C++11的<random>头文件生成随机数；2. 通过std::random_device初始化种子；3. 使用std::mt19937作为随机数引擎；4. 用std::uniform_int_distribution设置范围；5. 生成1到100之间的随机整数，避免rand()的低质量和范围限制，该方法更可靠且灵活。

Here's a practical example of generating random numbers in C++ using modern C++ techniques (C++11 and later):

Generating Random Numbers in C++

Instead of using the old rand() function, C++11 introduced the <random> header, which provides better randomness and more control.

Example: Generate a Random Integer Between 1 and 100

#include <iostream>
#include <random>

int main() {
    // Step 1: Create a random device to seed the generator
    std::random_device rd;

    // Step 2: Create a Mersenne Twister generator
    std::mt19937 gen(rd());

    // Step 3: Define a distribution (here, integers from 1 to 100)
    std::uniform_int_distribution<int> dist(1, 100);

    // Generate and print 5 random numbers
    for (int i = 0; i < 5; ++i) {
        int random_num = dist(gen);
        std::cout << random_num << " ";
    }
    std::cout << std::endl;

    return 0;
}

Output example:

42 7 98 34 65

Key Components Explained

• std::random_device rd;
  A true random number generator (if available) used to seed the generator. Good for unpredictable seeds.

• std::mt19937 gen(rd());
  The Mersenne Twister engine — a high-quality pseudo-random generator. mt19937 is widely used and much better than rand().

  

• std::uniform_int_distribution<int> dist(1, 100);
  Ensures numbers are uniformly distributed between 1 and 100 (inclusive).

Bonus: Random Floating-Point Number (0.0 to 1.0)

std::uniform_real_distribution<double> dist(0.0, 1.0);
double random_float = dist(gen);
std::cout << random_float << std::endl;

Why Not rand()?

• rand() has poor randomness quality.
• Limited range (RAND_MAX is often only 32767).
• std::random is easier to use with proper ranges and distributions.

Basically, use <random> with mt19937 and a distribution — it's more reliable and flexible.

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