function quicksortDijkstra(arr) {
  var N = arr.length,
      actions = [];

  //recursive sort call with n*log(n) average case complexity
  function sort(a, lo, hi) {
    if(lo >= hi) return;
    
    var lt = lo,
        i = lo + 1,
        gt = hi,
        v = a[lo]; // partition value

    while(i <= gt) { // elements i through gt are unexamined
      var diff = a[i] - v;
      if (diff < 0) swap(a, lt++, i++);
      else if (diff > 0) swap(a, i, gt--);
      else {
        i++; // equal to key, do keep contiguous stretch going
      }
      actions.push({type: "partition", lo: lo, lt: lt, i: i, gt: gt, hi: hi});
    }
    sort(a, lo, lt - 1);
    sort(a, gt + 1, hi);
  }

  function swap(arr, i, j) {
    var t = arr[i];
    arr[i] = arr[j];
    arr[j] = t;
    actions.push({type: "swap", i: i, j: j});
  }

  sort(arr, 0, N-1);

  return actions;
}

// Node or browser?
if (typeof window === 'undefined') {
  module.exports = quicksort;

} else {
  window.quicksortDijkstra = quicksortDijkstra;
}