>>不明白 vs BLOG>>

调用C++标准库中的函数实现：
#include
#include
#include "windows.h"
using namespace std;
template

void permutation(BidirectionalIterator first, BidirectionalIterator last,T s)
{
 sort(first,last);
 do{
  for(BidirectionalIterator i(first);i!=last;++i)
  {
   cout << *i; cout << s;
  }
  cout << endl;
 }while (next_permutation(first, last));
}

int main()
{
 int A[] = {1,2,3,4,5,6,7,8};
 const int N = sizeof(A) / sizeof(int);
 int nTime = GetTickCount();
 permutation(A, A+N ,",");
 nTime = GetTickCount() - nTime;

 return 0;
}

非递归实现：
#include "stdio.h"
#include "iostream.h"
#include "Windows.h"
void func(int n,char * a);
int main()
{
 char arr[]="12345678";
 int nTime = GetTickCount();
 func(8,arr);
 nTime = GetTickCount() - nTime;
 
 return 0;
}

void func(int n,char * a) //an array a[n]
{
 int *i=new int[n];
 int c=0,j;
 i[c]=-1;
 for(;i[0] {
  if(++i[c]  {
   for(j=0;j   if(j==c)
   {
    if(c+1    {
     i[++c]=-1;
     //  continue;
    }
    else
    {
     for(int j=0;j      cout<     cout<    }
   }
  }
  else
   c--;
 }
}

递归算法：
#include
#include "windows.h"

#define MAXN 100
int a[MAXN];
int flag[MAXN];

void comb(int m, int k, int s)
{
 int i;
 
 if (s >= k)
 {
  for (i = 0; i < k; i++)
   cout << a[i] << " ";
  cout << endl;
 }
 else
 {
  for (i = 1; i <= m; i++)
   if (0 == flag[i])
   {
    flag[i]=1;
    a[s]=i;
    comb(m,k,s+1);
    a[s]=0;
    flag[i]=0;
   }
 }
}

void main()
{
 int i;
 
 for (i=0; i  a[i]=flag[i]=0;
 
 int nTime = GetTickCount();
 comb(8,8,0);
 //comb(m,n,0) 表示求m个选n个的排列
 nTime = GetTickCount() - nTime;

 return;
}

以8个数的全排列来测试，递归最快，调用库函数最慢。

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