n 取 r 逆時鐘旋轉排列法

#include <functional>   // std::function
#include <memory>       // std::shared_ptr
#include <vector>
#include <iostream>

using namespace std;

// n 取 r 做排列 
// 採用逆時旋轉排列法
// 必須 n >= r
class Permutation_nPr
{
  // 回報結果
  function<void(const shared_ptr<vector<unsigned char> > &, size_t)> m_Report; 
  // 放置要排列的數字
  shared_ptr <vector<unsigned char> > m_Digital_Array;
  // 要做排列的數目值
  size_t m_r;

  void v(size_t n, size_t r)
  {
    size_t i = n + 1;
    while (i--)
    {
      if (r == 0)
        m_Report(m_Digital_Array, m_r);
      else
        v(n - 1, r - 1);
      unsigned char tmp = m_Digital_Array->at(n);
      for (size_t j = n; j > 0; --j)
        m_Digital_Array->at(j) = m_Digital_Array->at(j - 1);
      m_Digital_Array->at(0) = tmp;
    }
  }

public:
  Permutation_nPr(
     const function<void(const shared_ptr<vector<unsigned char> > &, size_t)> 
      &Receive
  )
     :m_Report(Receive)

  {}

  void nPr(size_t n, size_t r)
  {
    m_r = r;

    m_Digital_Array = 
       shared_ptr<vector<unsigned char> >(new vector<unsigned char>(n));
    size_t i = n;
    while (i--)
    {
      m_Digital_Array->at(i) = i;
    }

    v(n - 1, r - 1);
  }
};

int N = 1;
void Show(const shared_ptr<vector<unsigned char> > &Digital_Array, size_t r)
{
  cout << N << ":\t";

  for (size_t i = Digital_Array->size() - 1; r > 0; --i, --r)
    cout << (int)Digital_Array->at(i) << ' ';
  cout << endl;
  ++N;
}

int main()
{
  Permutation_nPr P(Show);

  cout << "4P3 排列：" << endl;
  N = 1;
  P.nPr(4, 3);

  return 0;
}

執行結果：

4P3 排列：
1:      3 2 1
2:      3 2 0
3:      3 1 0
4:      3 1 2
5:      3 0 2
6:      3 0 1
7:      2 1 0
8:      2 1 3
9:      2 0 3
10:     2 0 1
11:     2 3 1
12:     2 3 0
13:     1 0 3
14:     1 0 2
15:     1 3 2
16:     1 3 0
17:     1 2 0
18:     1 2 3
19:     0 3 2
20:     0 3 1
21:     0 2 1
22:     0 2 3
23:     0 1 3
24:     0 1 2
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