Create Validate Binary Search Tree.cpp

Author: daizhenyang

Validate Binary Search Tree.cpp

@@ -0,0 +1,42 @@
+/**
+ * Definition for binary tree
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    pair<pair<int,int>,bool>judge(TreeNode *root)
+    {
+        int mx=root->val;
+        int mi=mx;
+        bool r=true;
+        pair<pair<int,int>,bool>pl,pr;
+        if (root->left)
+        {
+            pl=judge(root->left);
+            mx=max(mx,pl.first.first);
+            mi=min(mi,pl.first.second);
+            r&=pl.second;
+            if (pl.first.first>=root->val)r=false;
+        }
+        if (root->right)
+        {
+            pr=judge(root->right);
+            mx=max(mx,pr.first.first);
+            mi=min(mi,pr.first.second);
+            r&=pr.second;
+            if (pr.first.second<=root->val)r=false;
+        }      
+        return make_pair(make_pair(mx,mi),r);
+    }
+    bool isValidBST(TreeNode *root) {
+        // Start typing your C/C++ solution below
+        // DO NOT write int main() function
+        if (!root)return true;
+        return judge(root).second;
+    }
+};