Create 333. Largest BST Subtree.cpp

Author: fengvyi

C++/333. Largest BST Subtree.cpp

@@ -0,0 +1,26 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    int largestBSTSubtree(TreeNode* root) {
+        int res = 0;
+        dfs(root, res);
+        return res;
+    }
+    
+    vector<int> dfs(TreeNode* root, int& res){
+        if(!root) return {INT_MAX, INT_MIN, 0};
+        auto l = dfs(root->left, res);
+        auto r = dfs(root->right, res);
+        int count = (l[2] == -1 || r[2] == -1 || l[1] >= root->val || r[0] <= root->val) ? -1 : l[2] + r[2] + 1;
+        res = max(res, count);
+        return {min(root->val, min(l[0], r[0])), max(root->val, max(l[1], r[1])), count};
+    }
+};