学步园

    题目大意：从n（1,2,3,4，，，n）个数字中取出来r个数字，输出全排列并且输出全排列的个数。

   代码：

# include<cstdio>
# include<iostream>
# include<cstring>
# include<iomanip>

using namespace std;

int a[1000];
int vis[1000];
int ans = 0;
int n,r;


void print()
{
    ans++;
    for ( int i = 1;i <= r;i++ )
        {
            cout<<setw(3)<<a[i];
        }
        cout<<endl;
}

int search( int t )
{
    for ( int i = 1;i <= n;i++ )
        {
            if (!vis[i])
                {
                    a[i] = t;
                    vis[i] = 1;
                        if ( t==r )
                            print();
                            else
                                search(t+1);
                            vis[i] = 0;
                }
        }
}

int main(void)
{
   // int n,r;
   memset(a,0,sizeof(a));
   memset(vis,0,sizeof(vis));
    cin>>n>>r;
    search(1);
    cout<<"number = "<<ans<<endl;


    return 0;
}