code: function (array, c, depth) {
          var start = array.length - (array.length / Math.pow(2, depth));
          for (var i = start, len = array.length; i < len; i += 1) {
              array[i] += c;
          }
      }
docs: Add a char to certain elements of an array.
  
  @param {Array} array An array of strings
  @param {String} c A string to add to each string
  @param {Number} depth The current binary tree depth to add to.
  @api private