Validate Binary Search Tree

最新推荐文章于 2024-10-14 16:31:29 发布

brucehb

最新推荐文章于 2024-10-14 16:31:29 发布

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本文介绍了一种判断二叉树是否为有效二叉搜索树的方法。通过递归检查每个节点的值是否在其允许范围内，确保左子树的值小于节点值且右子树的值大于节点值。

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 be binary search trees.

struct Node
{
	int val;
	Node(int v)
	{
		val = v;
		left = right = NULL;
	}
	Node *left;
	Node *right;
};

bool visit(Node *root, int leftMargin, int rightMargin)
{
	if (root == NULL)
	{
		return true;
	}
	
	return (root->val < rightMargin && root->val > leftMargin) 
			&& visit(root->left, leftMargin, root->val) 
			&& visit(root->right, root->val, rightMargin);
}

bool valid(Node *root)
{
	return visit(root, INT_MIN, INT_MAX);
}