stl random_shuffle

不多说，多看点书总归是好的，不要看了一半就扔了

template <class RandomAccessIterator>
  void random_shuffle (RandomAccessIterator first, RandomAccessIterator last);

template <class RandomAccessIterator, class RandomNumberGenerator>
  void random_shuffle (RandomAccessIterator first, RandomAccessIterator last,RandomNumberGenerator& gen);

关注源码是如何实现的

template <class RandomAccessIterator, class RandomNumberGenerator>
void random_shuffle (RandomAccessIterator first, RandomAccessIterator last,RandomNumberGenerator& gen)
{
  iterator_traits<RandomAccessIterator>::difference_type i, n;
  n = (last-first);
  for (i=n-1; i>0; --i) 
  {
    swap (first[i],first[gen(i+1)]);
  }
}

// random_shuffle example
#include <iostream>     // std::cout
#include <algorithm>    // std::random_shuffle
#include <vector>       // std::vector
#include <ctime>        // std::time
#include <cstdlib>      // std::rand, std::srand

// random generator function:
int myrandom (int i) { return std::rand()%i;}

int main () {
  //另外需要配合srand来使用，否则执行多次的结果是一样的
  std::srand ( unsigned ( std::time(0) ) );
  std::vector<int> myvector;

  // set some values:
  for (int i=1; i<10; ++i) myvector.push_back(i); // 1 2 3 4 5 6 7 8 9

  // using built-in random generator:
  std::random_shuffle ( myvector.begin(), myvector.end() );

  // using myrandom:
  std::random_shuffle ( myvector.begin(), myvector.end(), myrandom);

  // print out content:
  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;

  std::cout << '\n';

  return 0;
}

代码示例来自于http://www.cplusplus.com/reference/algorithm/random_shuffle/