check in the code

By Algorithms/Leetcode 501 Find mode in binary search tree/Leetcode 501 Find mode in binary search tree - in order traversal - ShortVersion.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Leetcode501_FindModeInBST
+{
+    /// <summary>
+    /// Leetcode 501 - Find mode in BST
+    /// Study discussion panel:
+    /// https://leetcode.com/problems/find-mode-in-binary-search-tree/discuss/98101/Proper-O(1)-space
+    /// Simplify the logic, every visit of node - update the mode
+    /// </summary>
+    class Program
+    {
+        public class TreeNode
+        {
+            public int val;
+            public TreeNode left;
+            public TreeNode right;
+            public TreeNode(int x) { val = x; }
+        }
+
+        static void Main(string[] args)
+        {
+            //RunSampleTestcase();  
+            RunTestCase();
+        }
+
+        public static void RunSampleTestcase()
+        {
+            var root1 = new TreeNode(1);
+            var root2 = new TreeNode(2);
+            var root2B = new TreeNode(2);
+            root1.right = root2;
+            root2.left = root2B;
+
+            var result = FindMode(root1);
+        }
+
+        public static void RunTestCase()
+        {
+            var root1 = new TreeNode(1);
+            var root2 = new TreeNode(2);
+
+            root1.right = root2;
+
+            var result = FindMode(root1);
+        }
+
+        public static TreeNode previous;
+        public static TreeNode current;
+        public static int max = 0;
+
+        public static int currentCount = 0;
+        public static HashSet<int> numbers;
+
+        public static int[] FindMode(TreeNode root)
+        {
+            previous = null;
+            current = null;
+            max = 0;
+
+            currentCount = 0;
+            numbers = new HashSet<int>();
+
+            inorderTraversal(root);
+
+            return numbers.ToArray();
+        }
+
+        /// <summary>
+        /// inorder traversal - left, root, right 
+        /// </summary>
+        /// <param name="root"></param>
+        private static void inorderTraversal(TreeNode root)
+        {
+            if (root == null)
+            {
+                return;
+            }
+
+            inorderTraversal(root.left);
+
+            // handling mode rules 
+            current = root;
+            var sameAsPrevious = previous != null && previous.val == current.val;
+            var startNew = previous == null || previous.val != current.val;            
+
+            if (sameAsPrevious)
+            {
+                currentCount++;                
+            }
+
+            if (startNew)
+            {                                                
+                currentCount = 1;                
+            }
+
+            // every node the mode is checked to simplify the code logic
+            updateMode(current.val);
+
+            // set current to previous
+            previous = current;
+
+            inorderTraversal(root.right);
+        }
+
+        /// <summary>
+        /// 
+        /// </summary>
+        private static void updateMode(int candidate)
+        {
+            // summarize the last value               
+            if (currentCount > max)
+            {
+                max = currentCount;
+
+                numbers.Clear();
+                numbers.Add(candidate);
+            }
+            else if (currentCount > 0 && currentCount == max)
+            {
+                numbers.Add(candidate);
+            }
+        }
+    }
+}