Null or Cycle

Entertainment Unit · December 22nd, 2014, 05:34 PM

I like my solution a little better than the book's:

Code:

// Javascript
function isCycle(list) {
  var slow,
      fast;

  slow = fast = list;

  while (fast.next) {
    slow = slow.next;
    fast = fast.next && fast.next.next;

    if (slow === fast || fast.next === slow) {
      return true;
    }
  }
  return false;
}

Fewer ifs and elses and sometimes while (true) can be a code smell.

Entertainment Unit · December 22nd, 2014, 05:59 PM

Quote:

Originally Posted by Entertainment Unit

I like my solution a little better than the book's:

Code:

// Javascript
function isCycle(list) {
  var slow,
      fast;

  slow = fast = list;

  while (fast.next) {
    slow = slow.next;
    fast = fast.next && fast.next.next;

    if (slow === fast || fast.next === slow) {
      return true;
    }
  }
  return false;
}

Fewer ifs and elses and sometimes while (true) can be a code smell.

Ha, except I just realized it doesn't work for lists that have an even number of elements. Better:

Code:

function isCycle(list) {
  var slow,
      fast;

  slow = fast = list;

  while (fast.next) {
    slow = slow.next;
    fast = fast.next && fast.next.next;

    if (!fast) {
      return false;
    }

    if (slow === fast || fast.next === slow) {
      return true;
    }
  }
  return false;
}

The learning process illustrated!