递归-全排列

对数组{1,2,3}进行全排列

#include <iostream>
using namespace std;
void swap(int a[],int i,int j)
{
    int tmp = a[i];
    a[i] = a[j];
    a[j] = tmp;
}
void printArray(int a[],int n)
{
    for(int i=0; i<n; i++)
        cout<<a[i]<<" ";
    cout<<endl;
}
void perm(int a[],int p,int q)
{
    if(p==q)
        printArray(a,q+1);
    for(int i=p; i<=q; i++)
    {
        swap(a,p,i);
        perm(a,p+1,q);
        swap(a,p,i);
    }
}
int main()
{
    int a[] = {1,2,3};
    perm(a,0,2);
    return 0;
}

STL next_permutation

#include <algorithm>
int main()
{
    int a[] = {1,2,3};
    //perm(a,0,2);
    do
    {
        for(int i=0;i<3;i++)
            cout<<a[i]<<" ";
        cout<<endl;
    }while(next_permutation(a,a+3));
    return 0;
}