freeCodeCamp Challenge Guide: No Repeats Please

Guide
25

This was INTENSE! By far the hardest algorithm so far I think… this one made me feel like an absolute novice.
After much deliberation ended up implementing a non-recursive version of Heap’s algorithm…

  let n = str.length
  let array = str.split('')
  let count = 0;

  let checkRepeats = (x) => {
  return  /(.)+\1/g.test(x.join('')) 
  }
  
  let c = [];
  for(let i = 0; i < n; i++){
    c[i] = 0
  }
  
  checkRepeats(array) ? null : count++
  
  let i = 0;
  while(i < n){
    if(c[i] < i){
      if(i % 2 == 0){
        [array[0], array[i]] = [array[i], array[0]]
      } else {
        [array[c[i]], array[i]] = [array[i], array[c[i]]]
      }
      checkRepeats(array) ? null : count++
      c[i] += 1
      i = 0
    } else {
      c[i] = 0
      i++
    }
  }
return count
}
2 Likes