Method update

Data-Structures/Heap/KeyPriorityQueue.js:78–96

* Updates the priority of the given element. * Adds the element if it is not in the queue. * @param {*} key the element to change * @param {number} priority new priority of the element

(key, priority)

   * @param {number} priority new priority of the element
   */
  update(key, priority) {
    const currPos = this._heap.indexOf(key)
    // if the key does not exist yet, add it
    if (currPos === -1) return this.push(key, priority)
    // else update priority
    this.priorities.set(key, priority)
    const parentPos = getParentPosition(currPos)
    const currPriority = this._getPriorityOrInfinite(currPos)
    const parentPriority = this._getPriorityOrInfinite(parentPos)
    const [child1Pos, child2Pos] = getChildrenPositions(currPos)
    const child1Priority = this._getPriorityOrInfinite(child1Pos)
    const child2Priority = this._getPriorityOrInfinite(child2Pos)

    if (parentPos >= 0 && parentPriority > currPriority) {
      this._shiftUp(currPos)
    } else if (child1Priority < currPriority || child2Priority < currPriority) {
      this._shiftDown(currPos)
    }
  }

  _getPriorityOrInfinite(position) {
    // Helper function, returns priority of the node, or Infinite if no node corresponds to this position