Stuck on "No repeats please"

JavaScript
1

Since I’ve been trying on my own for way too long I decided to finally take a hint. I saw here that I could solve it recursively (which had crossed my mind before, when I was trying on my own, so I thought I’d implement that one). I’m trying to implement the provided pseudocode but I’m a bit stuck.

var str = ???;
permAlone(current position in original string, characters used already in original string, created string) {
  if (current string is finished) {
    print current string;
  } else {
    for (var i = 0; i < str.length; i++) {
      if (str[i] has not been used) {
        put str[i] into the current position of new string;
        mark str[i] as used;
        permAlone(current position in original string, characters used already in original string, created string);
        remove str[i] as used because another branch in the tree for i + 1 will likely use it;
      }
    }
  }
}
permAlone(0, nothing used yet, empty new string (or array the same size as str));

My code so far is:

function permAlone(str) {
  var num = 0;
  var combos = [];
  var c = 0;
  str = str.split("");
  function perms(pos,used,combo){
    if(combo.length==str.length){
      combos.push(combo);
    }else{
      for(var i=0;i<str.length;i++){
        if(used.indexOf(i)==-1){
          //var curr = "";
          //combo = [];
          //curr[pos]=str[i];
          combo[pos]=str[i];
          //curr.concat(str[i]);
          used.push(i);
          perms(pos,used,combo);
          used.push(i);
        }
        //pos++;
      }
    }     
  }
  perms(0,[],[]);
  return num;
}

Specifically, I’m not sure if I use pos right and also I’m not sure if I intepret put str[i] into the current position of new string;and remove str[i] as used because another branch in the tree for i + 1 will likely use it; correctly. Note that the commented lines are the ones I’m not sure if I should include (by themselves or in place of other similar )or where should I put them (like pos++). In the end I always get an empty combos array.
Am I on the right track? Are there any details I’ve missed? Any suggestions would be appreciated!

2

Hi,
This is kind of a complicated challenge. You might want to break it up into parts and also work out some expected results on paper. The link in the challenge to the mathisfun site was very helpful.

I would suggest you attempt to get all permutations first. Console.log those so you can see if your function(s) is calculating what is expected. Once you have successfully figured out how to get all permutations then you can work on eliminating those with consecutive duplicate letters. Then you can count the remaining permutations.

What you have right now is a function that sets num=0 then returns num. Without any output it is hard to trace.

Divide and conquer. Good luck!

3

I had used that method before I got the hint. With my code as it is now combos is an empty array every time. I need more specific suggestions on my code.