Port to netstandard.

Nit fixes.
Fixed e2e tests.
Added MIT license.

SystemExtensions.NetStandard/Collections/PriorityQueue.cs

@@ -0,0 +1,103 @@
+namespace System.Collections.Generic
+{
+    /// <summary>
+    /// Priority Queue data structure. The implementation is based on an array-based implementation of Binary Heap.
+    /// Exposes some of the functionality of the Binary Heap as a queue.
+    /// </summary>
+    /// <typeparam name="T">Provided type.</typeparam>
+    [Serializable]
+    public sealed class PriorityQueue<T> : IQueue<T> where T : IComparable<T>
+    {
+        #region Fields
+        private readonly BinaryHeap<T> binaryHeap;
+        #endregion
+        #region Properties
+        /// <summary>
+        /// Returns the number of elements stored into the queue.
+        /// </summary>
+        public int Count
+        {
+            get
+            {
+                return binaryHeap.Count;
+            }
+        }
+        #endregion
+        #region Constructors
+        /// <summary>
+        /// Constructor for priority queue data structure.
+        /// </summary>
+        public PriorityQueue()
+        {
+            binaryHeap = new BinaryHeap<T>();
+        }
+        #endregion
+        #region Public Methods
+        /// <summary>
+        /// Add provided value to the queue.
+        /// </summary>
+        /// <param name="value">Value to be added to the queue.</param>
+        public void Enqueue(T value)
+        {
+            binaryHeap.Add(value);
+        }
+        /// <summary>
+        /// Pops the queue and removes the highest priority value from the queue.
+        /// </summary>
+        /// <returns>Highest priority value from the queue</returns>
+        public T Dequeue()
+        {
+            if (Count > 0)
+            {
+                return binaryHeap.Remove();
+            }
+            else
+            {
+                throw new IndexOutOfRangeException("Queue is empty!");
+            }
+        }
+        /// <summary>
+        /// Looks up the highest priority value from the queue. Doesn't alter the queue in any way.
+        /// </summary>
+        /// <returns>Highest priority value from the queue.</returns>
+        public T Peek()
+        {
+            return binaryHeap.Min;
+        }
+        /// <summary>
+        /// Clears the queue contents, removing any value stored into the queue.
+        /// </summary>
+        public void Clear()
+        {
+            binaryHeap.Clear();
+        }
+        /// <summary>
+        /// Checks if queue contains provided item.
+        /// </summary>
+        /// <param name="item">Item to be checked.</param>
+        /// <returns>True if queue contains the provided item. False otherwise.</returns>
+        public bool Contains(T item)
+        {
+            return binaryHeap.Contains(item);
+        }
+        /// <summary>
+        /// Returns an enumerator that iterates over the queue.
+        /// </summary>
+        /// <returns>Enumerator that iterates over the queue.</returns>
+        public IEnumerator<T> GetEnumerator()
+        {
+            return binaryHeap.GetEnumerator();
+        }
+        #endregion
+        #region Private Methods
+        /// <summary>
+        /// Necesarry for the implementatio of IQueue.
+        /// </summary>
+        /// <returns></returns>
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            throw new NotImplementedException();
+        }
+        #endregion
+    }
+}