next_permutation(start, end)

#include <iostream>
#include <algorithm>
#include <iterator>

using namespace std;

void p(char * a, const int m){
    do{
        copy(a, a+m+1, ostream_iterator<char>(cout," "));
        cout<<endl;
    }while(next_permutation(a,a+m+1));
}
int main() {
    char a[3]={'1','2','3'};
    p(a,2);
    return 0;
}