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### by Sumit Chourasia | Oct 07, 2020 | Category :coding | Tags : algorithmbinary-treedata-structureeasyleetcodetree #### Find Mode in Binary Search Tree - Tree - Easy - LeetCode

Given a binary search tree (BST) with duplicates, find all the mode(s) (the most frequently occurred element) in the given BST.

Assume a BST is defined as follows:

The left subtree of a node contains only nodes with keys less than or equal to the node's key.
The right subtree of a node contains only nodes with keys greater than or equal to the node's key.
Both the left and right subtrees must also be binary search trees.

For example:
Given BST [1,null,2,2],

1
\
2
/
2

return .

Note: If a tree has more than one mode, you can return them in any order.

Follow up: Could you do that without using any extra space? (Assume that the implicit stack space incurred due to recursion does not count).

``````/**
* 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 {
int? prev = null;
int count = 1;
int max = 0;
public int[] FindMode(TreeNode root) {
var list = new List<int>();
InOrder(root,list);
return list.ToArray();
}

private void InOrder(TreeNode root, List<int> list){
if(root==null){
return;
}

InOrder(root.left, list);

if(prev != null){
if(root.val==prev){
count++;
}
else{
count = 1;
}
}

if(count>max){
max = count;
list.Clear();
}
else if(count == max){