帮忙看看，分治法求全排列，这个程序运行时间太长，要怎么改？？ - 编程论坛

程序代码：

#include <cstring>
#include <iostream>
#include <stdio.h>
using namespace std;
#define N 4
char str[10];
void Perm(char *str, int k, int m);
void Swap(char &a, char &b);
int main()
{
     int n;
     while(scanf("%d", &n) != EOF)
     {
            for(int i=0; i<=n; ++i)
            {
                 str[i] = i+'0';
            }
            Perm(str, 1, n);
     }
     return 0;
}
void Perm(char *str, int k, int m)
{
     int i;
     if(k == m)
     {
            for(i=1; i<=m; ++i)
            cout<<str[i]<<" "<<flush;
            cout<<endl;
            return;
     }
     for(i=k; i<=m; ++i)
     {
            Swap(str[k], str[i]);
            Perm(str, k+1, m);
            Swap(str[k], str[i]);
     }
}
void Swap(char &a, char &b)
{
     char tmp = a;
     a = b;
     b = tmp;
}