"Leetcode-Interview algorithm classic-java implementation" "098-validate Binary search tree (verify binary searching trees)"

"098-validate binary search Tree" "leetcode-Interview algorithm classic-java Implementation" "All topics Directory Index" Original Question

Given a binary tree, determine if it is a valid binary search tree (BST).
Assume a BST is defined as follows:
The left subtree of a node contains only nodes with keys less than the node ' s key.
The right subtree of a node contains only nodes with keys greater than the node ' s key.
Both the left and right subtrees must also is binary search trees.

Main Topic

Verify binary search tree

Thinking of solving problems

The two-fork search tree is sequenced, the results are saved sequentially, and the result of the sequential traversal of the binary search tree is a small-to-large sequence, and there is no heavy elements, which can be used to determine whether a tree is a two-fork search tree.

Code Implementation

Tree Node class

publicclass TreeNode {    int val;    TreeNode left;    TreeNode right;    TreeNode(int x) { val = x; }}

Algorithm implementation class

ImportJava.util.Stack; Public  class solution {    PrivateStack<integer> Stack; Public Boolean Isvalidbst(TreeNode Root) {if(Root = =NULL) {return true; } stack =NewStack<> (); Inorder (root);inti = Stack.pop ();intJ while(!stack.isempty ()) {j = Stack.pop ();if(I <= J) {return false;        } i = J; }return true; }/** * If it is a binary search tree must be ordered * @param root * /     Public void inorder(TreeNode Root) {if(Root! =NULL) {inorder (root.left);            Stack.push (Root.val);        Inorder (Root.right); }    }}

Evaluation Results

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"leetcode-Interview algorithm classic-java implementation" "098-validate binary search tree (validating binary searching trees)"