Repenting for my sins

perm.groovy

/*
Once upon a time I got an interview with CosmicCart. I had a skype call at 7am but totally forgot about it
and went out drinking the previous night. I got home at 4am very drunk, got up at 6:30 with a killing 
hangover and totally flunked that interview. 

I finished the 2 element permutation, then he asked me to do the 3 element combination
and I couldn't think straight to solve it.

This is my repentance. I'll get to the n-element method and cleanse my soul.

*/


def lsto = [1,2,3,4]

def perm2(out, lst){
    if(lst.size() == 1) return out
    def p1 = lst.pop()
    lst.each{
        out << [p1,it]
    }
    return perm2(out, lst)
}

def perm3(out,pairs,lst){
    if(lst.size() == 0) return out;
    def piv = lst.pop()
    pairs.each{
        if(!(piv in it)){
            out << it + piv
        }
    } 

    return perm3(out,pairs,lst)
}

def perm4(groups,lst){

}

def permn(n, groups, lst){
    
}

def pairs = perm2([], lsto.clone())
perm3([],pairs,lsto.clone())