判断BST是否合法

Validate Binary Search Tree/Validate Binary Search Tree.c

@@ -0,0 +1,30 @@
+//leetcode oj 98
+//https://leetcode.com/problems/validate-binary-search-tree/description/
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     struct TreeNode *left;
+ *     struct TreeNode *right;
+ * };
+ */
+bool foo(struct TreeNode* root,long int *bar)
+{
+    if(!root)
+    {
+        return true;
+    }
+    bool _ = foo(root->left,bar);
+    if(root->val<=*bar)
+    {
+        return false;
+    }
+    *bar = root->val;
+    bool __ = foo(root->right,bar);
+    return _ && __;
+}
+bool isValidBST(struct TreeNode* root) 
+{
+    long int _ = LONG_MIN;
+    return foo(root,&_);
+}