validate-bin-search-tree

Author: dylan-jung

validate-binary-search-tree/dylan-jung.cpp

@@ -0,0 +1,29 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+ class Solution {
+public:
+    bool dfs(TreeNode* root, long minVal, long maxVal) {
+        if(!(minVal < root->val && root->val < maxVal)) return false;
+        bool isValid = true;
+        if(root->left) {
+            isValid = isValid && dfs(root->left, minVal, min((long)root->val, maxVal));
+        }
+        if(root->right) {
+            isValid = isValid && dfs(root->right, max((long)root->val, minVal), maxVal);
+        }
+        return isValid;
+    }
+
+    bool isValidBST(TreeNode* root) {
+        return dfs(root, -(1l << 32), 1l << 32);
+    }
+};