c++_primer_exercise_1728_1729_1730

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最新推荐文章于 2023-08-07 08:41:47 发布

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分类专栏： C++Primer6thExe

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本文介绍如何使用C++生成均匀分布的随机数，并通过一个具体示例演示了如何统计这些随机数出现的频率。文章包括了必要的代码实现及解释。

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/*************************************************
 * IDE: VS2010
 *************************************************/
#include 
using std::cin; using std::cout; using std::endl;

#include 
using std::vector;

#include 
using std::map;

#include 
using std::default_random_engine;
using std::uniform_int_distribution;

// returns a vector of 100 uniformly distributed random numbers
vector rand_vec(unsigned long seed, unsigned min_val, unsigned max_val)
{
	// because engines and distributions retain state, they usually should be
	// defined as static so that new numbers are generated on each call
	static default_random_engine e(seed);
	static uniform_int_distribution u(min_val, max_val);
	vector ret;
	for (unsigned i = 0; i != 100; ++i)
	{
		ret.push_back(u(e));
	}
	return ret;
}


int main()
{
	vector v(rand_vec(255, 0, 9));
	map num_count;

	// count
	for (vector::iterator it = v.begin(); 
		 it != v.end(); ++it)
	{
		++num_count[*it];
	}

	// print
	for (map::iterator it = num_count.begin();
		 it != num_count.end(); ++it)
	{
		cout << it->first << " occurs " << it->second
			 << ((it->second > 1) ? " times" : " time") << endl;
	}

	return 0;
}