排列数算法A(n,m)(n>=m)

#include<iostream>
using namespace std;
int source[]={1,2,3,4,5,6,7,8,9},n=9,m=3,record[10],visited[10],counter=0;
void output()
{
	for(int i=0;i<m;i++)
		cout<<record[i]<<" ";
	cout<<endl;
}
void dfs(int step)
{
	if(step==m)
	{
		output();
		counter++;
		return ;
	}
	for(int i=0;i<n;i++)
	{
		if(visited[i]==0)
		{
			visited[i]=1;
			record[step]=source[i];
			dfs(step+1);
			visited[i]=0;
		}
	}
}
int main()
{
	dfs(0);
	cout<<counter<<endl;
	return 0;
}