随机洗牌

#pragma once
#include <vector>

class SelectedRandomCard
{
public:
	SelectedRandomCard(int n, int m);
	~SelectedRandomCard(void);

	std::vector<int> perform();

private:
	void randomPermutation();

private:
	int _totalN;
	int _selectedM;
	std::vector<int> _v;

};

#include "StdAfx.h"
#include "SelectedRandomCard.h"
#include <time.h>
#include <random>
#include <iostream>


SelectedRandomCard::SelectedRandomCard( int n, int m )
{
	_totalN = n;
	_selectedM = m;
	for (int i = 0; i<_totalN; i++)
	{
		_v.push_back(i);
	}

	srand((unsigned)time(NULL));
}

SelectedRandomCard::~SelectedRandomCard(void)
{
}

void SelectedRandomCard::randomPermutation()
{
	int temp = 0;
	int randomselected = 0;
	for (int i=0; i<_selectedM; i++)
	{
		//std::cout<<rand()<<std::endl;
		randomselected = rand()%(_totalN - i) + i;
		temp = _v[i];
		_v[i] = _v[randomselected];
		_v[randomselected] = temp;
	}
}

std::vector<int> SelectedRandomCard::perform()
{
	randomPermutation();
	return _v;
}

测试

// randomConsole.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "SelectedRandomCard.h"
#include <iostream>


int _tmain(int argc, _TCHAR* argv[])
{
	int vectorSize = 10;
	const int testN = 100000000;
	std::vector<int> sumV;
	//initialize the sumV
    for (int i=0; i<vectorSize; i++)
    {
		sumV.push_back(0);
    }

	for (int i = 0; i<testN; i++)
	{

		SelectedRandomCard sRandowCard(vectorSize,vectorSize);
		std::vector<int> randomSequence = sRandowCard.perform();

		for (size_t i=0; i<randomSequence.size(); i++)
		{
			sumV[i] += randomSequence[i];
			//std::cout<<randomSequence[i]<<std::endl;
		}

	}

	for (size_t i=0; i<sumV.size(); i++)
	{
		std::cout<<sumV[i]<<std::endl;
	}



	return 0;
}

测试算法很慢，并出现溢出，另外随机算法ｒａｎｄ有些问题。