全排列

#include"iostream"
#include"algorithm"
using namespace std;
int main()
{
        //prev_permutation 倒序
    int a[3]={3,2,1};
    do 
    {
        for(int i=0;i<3;i++)
            cout<<a[i]<<" ";
        cout<<endl;
    }while(prev_permutation(a,a+3));
    //输入结果
    /*
        3 2 1
        3 1 2
        2 3 1
        2 1 3
        1 3 2
        1 2 3
    */
    cout<<endl;
    
        //next_permutation  倒序
    int b[3]={1,2,3};
    do 
    {
        for(int i=0;i<3;i++)
            cout<<b[i]<<" ";
        cout<<endl;
    }while(next_permutation(b,b+3));
    //输入结果
    /*
        1 2 3
        1 3 2
        2 1 3
        2 3 1
        3 1 2
        3 2 1
    */ 
 }