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std::srand

STD：SRAND

Defined in header ​​
void srand( unsigned seed ​​

使用的伪随机数生成器种子。std::rand()有价值seed...

如果rand()在调用srand()，，，rand()表现得好像它是被播种的srand(1)...

每次rand()都是一样的seed，它必须产生相同的值序列。

srand()不能保证线程安全。

参数

seed-the seed value

返回值

%280%29

注记

一般情况下，伪随机数生成器只应在调用rand()，在节目开始的时候。它不应该被重复播种，或者每次你想要生成一批新的伪随机数时都被重新种植。

的标准做法是使用调用的结果time(0)就像种子一样。然而，time()返回time_t价值，和time_t不能保证是一个完整的类型。然而，在实践中，每个主要实现都定义了time_t成为一个完整的类型，这也是POSIX所要求的。

例

二次

#include <cstdlib>
#include <iostream>
#include <ctime>
 
int main() 
{
    std::srand(std::time(0) //use current time as seed for random generator
    int random_variable = std::rand(
    std::cout << "Random value on [0 " << RAND_MAX << "]: " 
              << random_variable << '\n';
}

二次

可能的产出：

二次

Random value on [0 2147483647]: 1373858591

二次

另见

randgenerates a pseudo-random number (function)
RAND_MAXmaximum possible value generated by std::rand (macro constant)
reseedreseeds the per-thread random engine (function)

c为瑞典兰德编写的文件

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