Add a basic Bag data structure

Author: kamikkels

DataStructures/Bag.cs

@@ -0,0 +1,75 @@
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace DataStructures;
+
+/// <summary>
+/// Implementation of a Bag data structure using a hashmap that allows adding items and iterating through them.
+/// Items with the same value are stored as a single entry with a count.
+/// </summary>
+/// <typeparam name="T">Generic Type.</typeparam>
+public class Bag<T> : IEnumerable<T> where T : notnull
+{
+    private readonly Dictionary<T, int> items;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Bag{T}" /> class.
+    /// </summary>
+    public Bag()
+    {
+        items = [];
+    }
+
+    /// <summary>
+    /// Adds an item to the bag.
+    /// </summary>
+    public void Add(T item)
+    {
+        if (items.TryGetValue(item, out var count))
+        {
+            items[item] = count + 1;
+        }
+        else
+        {
+            items[item] = 1;
+        }
+    }
+
+    /// <summary>
+    /// Clears the bag.
+    /// </summary>
+    public void Clear() => items.Clear();
+
+    /// <summary>
+    /// Gets the number of items in the bag.
+    /// </summary>
+    public int Count => items.Values.Sum();
+
+    /// <summary>
+    /// Returns a boolean indicating whether the bag is empty.
+    /// </summary>
+    public bool IsEmpty() => items.Count == 0;
+
+    /// <summary>
+    /// Returns an enumerator that iterates through the bag.
+    /// </summary>
+    public IEnumerator<T> GetEnumerator()
+    {
+        foreach (var pair in items)
+        {
+            for (var i = 0; i < pair.Value; i++)
+            {
+                yield return pair.Key;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Returns an enumerator that iterates through the bag.
+    /// </summary>
+    IEnumerator IEnumerable.GetEnumerator()
+    {
+        return GetEnumerator();
+    }
+}

README.md

@@ -247,6 +247,7 @@ find more than one implementation for the same objective but using different alg
       * [Levenshtein Distance](./Algorithms/Problems/DynamicProgramming/LevenshteinDistance/LevenshteinDistance.cs)
 
 * [Data Structures](./DataStructures)
+  * [Bag](./DataStructures/Bag.cs) 
   * [Bit Array](./DataStructures/BitArray.cs)
   * [Timeline](./DataStructures/Timeline.cs)
   * [Segment Trees](./DataStructures/SegmentTrees)