largest BST subtree

Author: fishercoder1534

MEDIUM/src/medium/LargestBSTSubtree.java

@@ -0,0 +1,39 @@
+package medium;
+
+import classes.TreeNode;
+
+public class LargestBSTSubtree {
+
+    public int largestBSTSubtree(TreeNode root) {
+        if(root == null) return 0;
+        if(isBST(root)) return getNodes(root);
+        return Math.max(find(root.left), find(root.right));
+    }
+    
+    int find(TreeNode root){
+        if(isBST(root)) return getNodes(root);
+        return Math.max(find(root.left), find(root.right));
+    }
+    
+    int getNodes(TreeNode root){
+        if(root == null) return 0;
+        return dfsCount(root);
+    }
+    
+    int dfsCount(TreeNode root){
+        if(root == null) return 0;
+        return dfsCount(root.left) + dfsCount(root.right) + 1;
+    }
+    
+    boolean isBST(TreeNode root){
+        if(root == null) return true;
+        return dfs(root, Long.MIN_VALUE, Long.MAX_VALUE);
+    }
+    
+    boolean dfs(TreeNode root, long min, long max){
+        if(root == null) return true;
+        if(root.val <= min || root.val >= max) return false;
+        return dfs(root.left, min, root.val) && dfs(root.right, root.val, max);
+    }
+
+}

README.md

@@ -39,7 +39,8 @@
 |349|[Intersection of Two Arrays](https://leetcode.com/problems/intersection-of-two-arrays/)|[Solution](../../blob/master/EASY/src/easy/IntersectionOfTwoArrays.java)| O(m+n)|O(min(m,n)) | Easy| Two Pointers, Binary Search
 |346|[Moving Average from Data Stream](https://leetcode.com/problems/moving-average-from-data-stream/)|[Solution](../../blob/master/EASY/src/easy/MovingAveragefromDataStream.java)| O(1)|O(w)) | Easy| Queue
 |339|[Nested List Weight Sum](https://leetcode.com/problems/nested-list-weight-sum/)|[Solution](../../blob/master/EASY/src/easy/NestedListWeightSum.java)| O(n)|O(h)) | Easy| DFS
-|338|[Counting Bits](https://leetcode.com/problems/counting-bits/)|[Solution](../../blob/master/MEDIUM/src/medium/CountingBits.java)| O(n)|O(n) | Medium| 
+|338|[Counting Bits](https://leetcode.com/problems/counting-bits/)|[Solution](../../blob/master/MEDIUM/src/medium/CountingBits.java)| O(nlogn)|O(h) | Medium| 
+|333|[Largest BST Subtree](https://leetcode.com/problems/largest-bst-subtree/)|[Solution](../../blob/master/MEDIUM/src/medium/LargestBSTSubtree.java)| O(n)|O(n) | Medium| 
 |325|[Maximum Size Subarray Sum Equals k](https://leetcode.com/problems/maximum-size-subarray-sum-equals-k/)|[Solution] | O(n)|O(n) | Medium| HashMap
 |314|[Binary Tree Vertical Order Traversal](https://leetcode.com/problems/binary-tree-vertical-order-traversal/)|[Solution](../../blob/master/MEDIUM/src/medium/BinaryTreeVerticalOrderTraversal.java)| O(n)|O(n) | Medium| HashMap, BFS
 |311|[Sparse Matrix Multiplication](https://leetcode.com/problems/sparse-matrix-multiplication/)|[Solution](../../blob/master/MEDIUM/src/medium/SparseMatrixMultiplication.java)| O(m*n*l)|O(m*l)| Medium|