No repeats please and Heap's algorithm

No repeats please

https://www.freecodecamp.com/challenges/no-repeats-please

Issue Description

I’m going nuts. Could someone please walk me through Heap’s algorithm? Why do we check int to see if it’s odd or even and why do we determine which elements to swap based on that? Where does this odd or even idea come from? Assuming that I don’t know this algorithm, how can I solve this challenge?

 function perm(str) {

  // Split the string into an array of characters.
  var arr = str.split('');
  var permutations = [];
  var tmp;

  // Function to swap variables' content.
  function swap(index1, index2) {
    tmp = arr[index1];
    arr[index1] = arr[index2];
    arr[index2] = tmp;
  }

  //Generate arrays of permutations using the algorithm.
  function generate(int) {      // int is length of array
    if (int === 1) {
      // Make sure to join the characters as we create  the permutation arrays
      permutations.push(arr.join(''));
    } else {
      for (var i = 0; i != int; ++i) {
        generate(int - 1);
        if (int % 2 === 0) {
          swap(i, int - 1);
        } else {
          swap(0, int - 1);
        }
      }
    }
  }

  generate(arr.length);

  return permutations;
}

console.log(perm("abcd"));

 

[dhcodes]

@fhdhsni maybe try again today?

[texas2010]

@Mongues looks like you may have accidentally subscribed to all notifications for the FreeCodeCamp repository. To stop receiving notifications please visit the subscriptions page and select “Not watching”. Additionally, you can visit the GitHub Help page on managing notification delivery methods for more help.

We are sorry for your inconvenience!