C++ 一条代码打印vector内容以及random_shuffle函数

#include <iostream>
#include <vector>
#include <iterator>
#include <algorithm>

using namespace std;

int main (int argc, char *argv[])
{
	int n = 10;
	vector<int> v;

	//append integers 0 to n-1 to v
	for (int i = 0; i < n; ++i) {
		v.push_back(i);
	}

	//random shuffle the values of v
	random_shuffle (v.begin(), v.end());
	//print all values of v to screen
	copy (v.begin(), v.end(), ostream_iterator<int> (cout, "\n"));

	return 0;
}

运行结果：
8
1
9
2
0
5
7
3
4
6
Press any key to continue . . .
     本实例简单演示了vector的使用，实际上该演示代码同时包含了迭代器（iterator）技术，如v.begin()和v.end(),
他们分别指示vector向量的初始化和末尾指针，同时该代码还采用了STL技术中的算法技术，通过STL算法函数
random_shuffle吧容器类的元素顺序捣乱，并通过算法函数copy实现数据的输出。
    有关以上程序的运行过程如下图所示，假设总共有100个元素，以上代码首先定义了一个空的vector对象，然后
赋值如第二步所示，第三步显示了赋值完毕后向量的存储实例，通过random_shuffle函数把容器类的元素顺序捣乱
后向量中存储的元素如第四步所示：
                   
关于random_shuffle函数详解如下：
一下内容出自：http://www.cplusplus.com/reference/algorithm/random_shuffle/

1.其函数原型如下：

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

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

该函数的功能是重新随机的排列first到last的间的所有元素。

Rearranges the elements in the range [first,last) randomly.

The function swaps the value of each element with that of some other randomly chosen element. When provided, the function rand chooses which element.

The behavior of this function template is equivalent to:
template <class RandomAccessIterator, class RandomNumberGenerator>
  void random_shuffle ( RandomAccessIterator first, RandomAccessIterator last,
                        RandomNumberGenerator& rand )
{
  iterator_traits<RandomAccessIterator>::difference_type i, n;
  n = (last-first);
  for (i=n-1; i>0; --i) swap (first[i],first[rand(i+1)]);
}

Parameters
first, last
Forward iterators to the initial and final positions of the sequence to be shuffled. The range used is [first,last), which contains all the elements between first andlast, including the element pointed by first but not the element pointed by last.
rand
Pointer to unary function taking one argument and returning a value, both of the appropriate difference type (generally ptrdiff_t). The function shall return a value between zero and its argument (lower than this).
Return value
none
Example

// random_shuffle example
#include <iostream>
#include <algorithm>
#include <functional>
#include <vector>
#include <ctime>
#include <cstdlib>
using namespace std;

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

// pointer object to it:
ptrdiff_t (*p_myrandom)(ptrdiff_t) = myrandom;

int main () {
  srand ( unsigned ( time (NULL) ) );
  vector<int> myvector;
  vector<int>::iterator it;

  // 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:
  random_shuffle ( myvector.begin(), myvector.end() );

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

  // print out content:
  cout << "myvector contains:";
  for (it=myvector.begin(); it!=myvector.end(); ++it)
    cout << " " << *it;

  cout << endl;

  return 0;
}

A possible output:
myvector contains: 3 4 1 6 8 9 2 7 5

others：
ptrdiff_t
Result of pointer subtraction
This is the type returned by the subtraction operation between two pointers. This is a signed integral type, and as such can be casted to compatible fundamental data types.
A subtraction of two pointers is only granted to have a valid defined value for pointers to elements of the same array (or for the element just past the last in the array).
For other values, the behavior depends on the system characteristics and compiler implementation.