我尝试着创造一款带有骰子的游戏，我需要在其中添加一些随机数字(游戏邦注:即模拟骰子的边缘)。我知道如何在1到6之间
#include <cstdlib>
#include <ctime>
#include <iostream>
using namespace std;
int main()
{
srand((unsigned)time(0));
int i;
i = (rand()%6)+1;
cout << i << "\n";
}
并不是很好地工作，因为当我运行程序几次，这是我得到的输出:
6
1
1
1
1
1
2
2
2
2
5
2
所以我想要一个每次生成不同随机数的命令，而不是连续5次生成相同的随机数。是否有这样的命令?
当前回答
可以从这里获得生成随机数的完整随机类代码!
如果你在项目的不同部分需要随机数，你可以创建一个单独的类Randomer来封装它里面的所有随机内容。
就像这样:
class Randomer {
// random seed by default
std::mt19937 gen_;
std::uniform_int_distribution<size_t> dist_;
public:
/* ... some convenient ctors ... */
Randomer(size_t min, size_t max, unsigned int seed = std::random_device{}())
: gen_{seed}, dist_{min, max} {
}
// if you want predictable numbers
void SetSeed(unsigned int seed) {
gen_.seed(seed);
}
size_t operator()() {
return dist_(gen_);
}
};
这样的类以后会很方便:
int main() {
Randomer randomer{0, 10};
std::cout << randomer() << "\n";
}
你可以检查这个链接作为一个例子，我如何使用这样的Randomer类生成随机字符串。如果你愿意，你也可以使用Randomer。
其他回答
#include <iostream>
#include <cstdlib>
#include <ctime>
int main() {
srand(time(NULL));
int random_number = std::rand(); // rand() return a number between 0 and RAND_MAX
std::cout << random_number;
return 0;
}
http://en.cppreference.com/w/cpp/numeric/random/rand
这段代码产生从n到m的随机数。
int random(int from, int to){
return rand() % (to - from + 1) + from;
}
例子:
int main(){
srand(time(0));
cout << random(0, 99) << "\n";
}
如果你正在使用boost lib，你可以通过以下方式获得一个随机生成器:
#include <iostream>
#include <string>
// Used in randomization
#include <ctime>
#include <boost/random/mersenne_twister.hpp>
#include <boost/random/uniform_int_distribution.hpp>
#include <boost/random/variate_generator.hpp>
using namespace std;
using namespace boost;
int current_time_nanoseconds(){
struct timespec tm;
clock_gettime(CLOCK_REALTIME, &tm);
return tm.tv_nsec;
}
int main (int argc, char* argv[]) {
unsigned int dice_rolls = 12;
random::mt19937 rng(current_time_nanoseconds());
random::uniform_int_distribution<> six(1,6);
for(unsigned int i=0; i<dice_rolls; i++){
cout << six(rng) << endl;
}
}
函数current_time_nanoseconds()给出以纳秒为单位的当前时间，用作种子。
下面是一个更通用的类，用于获取范围内的随机整数和日期:
#include <iostream>
#include <ctime>
#include <boost/random/mersenne_twister.hpp>
#include <boost/random/uniform_int_distribution.hpp>
#include <boost/random/variate_generator.hpp>
#include "boost/date_time/posix_time/posix_time.hpp"
#include "boost/date_time/gregorian/gregorian.hpp"
using namespace std;
using namespace boost;
using namespace boost::posix_time;
using namespace boost::gregorian;
class Randomizer {
private:
static const bool debug_mode = false;
random::mt19937 rng_;
// The private constructor so that the user can not directly instantiate
Randomizer() {
if(debug_mode==true){
this->rng_ = random::mt19937();
}else{
this->rng_ = random::mt19937(current_time_nanoseconds());
}
};
int current_time_nanoseconds(){
struct timespec tm;
clock_gettime(CLOCK_REALTIME, &tm);
return tm.tv_nsec;
}
// C++ 03
// ========
// Dont forget to declare these two. You want to make sure they
// are unacceptable otherwise you may accidentally get copies of
// your singleton appearing.
Randomizer(Randomizer const&); // Don't Implement
void operator=(Randomizer const&); // Don't implement
public:
static Randomizer& get_instance(){
// The only instance of the class is created at the first call get_instance ()
// and will be destroyed only when the program exits
static Randomizer instance;
return instance;
}
bool method() { return true; };
int rand(unsigned int floor, unsigned int ceil){
random::uniform_int_distribution<> rand_ = random::uniform_int_distribution<> (floor,ceil);
return (rand_(rng_));
}
// Is not considering the millisecons
time_duration rand_time_duration(){
boost::posix_time::time_duration floor(0, 0, 0, 0);
boost::posix_time::time_duration ceil(23, 59, 59, 0);
unsigned int rand_seconds = rand(floor.total_seconds(), ceil.total_seconds());
return seconds(rand_seconds);
}
date rand_date_from_epoch_to_now(){
date now = second_clock::local_time().date();
return rand_date_from_epoch_to_ceil(now);
}
date rand_date_from_epoch_to_ceil(date ceil_date){
date epoch = ptime(date(1970,1,1)).date();
return rand_date_in_interval(epoch, ceil_date);
}
date rand_date_in_interval(date floor_date, date ceil_date){
return rand_ptime_in_interval(ptime(floor_date), ptime(ceil_date)).date();
}
ptime rand_ptime_from_epoch_to_now(){
ptime now = second_clock::local_time();
return rand_ptime_from_epoch_to_ceil(now);
}
ptime rand_ptime_from_epoch_to_ceil(ptime ceil_date){
ptime epoch = ptime(date(1970,1,1));
return rand_ptime_in_interval(epoch, ceil_date);
}
ptime rand_ptime_in_interval(ptime floor_date, ptime ceil_date){
time_duration const diff = ceil_date - floor_date;
long long gap_seconds = diff.total_seconds();
long long step_seconds = Randomizer::get_instance().rand(0, gap_seconds);
return floor_date + seconds(step_seconds);
}
};
非常固执己见的回答
c++ <random>库违反了软件工程的最佳原则之一:“简单的事情做简单，复杂的事情，不寻常的事情可以更复杂一点。”
相反，他们甚至把简单和常见的用例变得过于复杂，只是因为他们患有文化疾病，害怕像“这还不够普遍”这样的评论。
As a result, now whenever you want a simple random number, you have to look into the documentation, read stack overflow with walls of text, glorifying this terrible design, instead of it just being an easy-to-remember one or 2 liner. (Common Lisp is more pragmatic: (random 5) yields uniformly distributed integers from 0..4 and (random 1.0) yields real numbers between 0.0..1.0. That is the most common use case and it is at your finger tips. If you need more sophisticated stuff, you have to find packages and libraries or do it yourself.)
只需计算一下全球范围内每个人浪费在理解标题及其内容上的时间累积的工时，就可以看到它有多糟糕。
即使我现在在浪费我的时间，写这个答案，你也在浪费时间，阅读它，只是因为他们创造了一个复杂的谜题，这与其他现代令人厌恶的东西相似，比如Vulkan API。
那么，如何应对呢?浪费一次时间，为自己最常见的用例编写一个头文件，然后在需要时重用它。
可以从这里获得生成随机数的完整随机类代码!
如果你在项目的不同部分需要随机数，你可以创建一个单独的类Randomer来封装它里面的所有随机内容。
就像这样:
class Randomer {
// random seed by default
std::mt19937 gen_;
std::uniform_int_distribution<size_t> dist_;
public:
/* ... some convenient ctors ... */
Randomer(size_t min, size_t max, unsigned int seed = std::random_device{}())
: gen_{seed}, dist_{min, max} {
}
// if you want predictable numbers
void SetSeed(unsigned int seed) {
gen_.seed(seed);
}
size_t operator()() {
return dist_(gen_);
}
};
这样的类以后会很方便:
int main() {
Randomer randomer{0, 10};
std::cout << randomer() << "\n";
}
你可以检查这个链接作为一个例子，我如何使用这样的Randomer类生成随机字符串。如果你愿意，你也可以使用Randomer。
