/*
    Detect a cycle in a Linked List.
    Note that the head may be 'null' if the list is empty.
    Node is defined as
    var Node = function(data) {
        this.data = data;
        this.next = null;
    }
*/

// This is a "method-only" submission.
// You only need to complete this method.

function hasCycle(head) {
//   console.log("starting...");
  var nodesToReset = [];
  var ret = false;
  for (var node = head; node != null; node = node.next) {
//     console.log("node.data = " + node.data + ", node.next.data = " + node.next.data + ", node.seen = " + node.seen);
    if (node.seen === true) {
      ret = true;
      break;
    }
    node.seen = true;
    nodesToReset.push(node);
  }
  nodesToReset.forEach(function(node) {
//     console.log("resetting node.data = " + node.data);
    node.seen = false;
  });
  return ret;
}