Merge pull request #2999 from dkiryanov/csharp/0958-check-completeness-of-a-binary-tree

Added a C# solution to 958. Check completeness of a binary tree

Author: Ykhan799

Diff for: csharp/0958-check-completeness-of-a-binary-tree.cs

@@ -0,0 +1,44 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution
+{
+    public bool IsCompleteTree(TreeNode root)
+    {
+        Queue<TreeNode> queue = new Queue<TreeNode>();
+        queue.Enqueue(root);
+
+        bool nullFound = false;
+
+        while (queue.Any())
+        {
+            TreeNode node = queue.Dequeue();
+
+            if (node is null)
+            {
+                nullFound = true;
+                continue;
+            }
+
+            if (nullFound)
+            {
+                return false;
+            }
+
+            queue.Enqueue(node.left);
+            queue.Enqueue(node.right);
+        }
+
+        return true;
+    }
+}