23. Merge k Sorted Lists

23. Merge k Sorted Lists/23. Merge k Sorted Lists.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <RootNamespace>_23._Merge_k_Sorted_Lists</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

23. Merge k Sorted Lists/ListNode.cs

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+
+public class ListNode
+{
+    public int val;
+    public ListNode? next;
+    public ListNode(int val = 0, ListNode? next = null)
+    {
+        this.val = val;
+        this.next = next;
+    }
+}

23. Merge k Sorted Lists/Program.cs

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+// See https://aka.ms/new-console-template for more information
+Console.WriteLine("Hello, World!");

23. Merge k Sorted Lists/Solution.cs

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+public class Solution
+{
+    public ListNode? MergeKLists(ListNode[] lists)
+    {
+        ListNode? head = null;
+        ListNode? tail = null;
+        var queue = new PriorityQueue<ListNode, int>();
+        foreach (var l in lists)
+            if (l != null)
+                queue.Enqueue(l, l.val);
+        while (queue.Count > 0)
+        {
+            var l = queue.Dequeue();
+            if (head == null || tail == null)
+            {
+                head = l;
+                tail = l;
+            }
+            else
+            {
+                tail.next = l;
+                tail = l;
+            }
+            if (l.next != null)
+                queue.Enqueue(l.next, l.next.val);
+        }
+        return head;
+    }
+}