Validate Binary Search Tree

验证二叉搜索树的有效性

最新推荐文章于 2024-10-14 16:31:29 发布

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本文探讨如何通过中序遍历的方式验证给定的二叉树是否为有效的二叉搜索树（BST）。通过递归地检查每个节点的值是否在特定的范围内，确保左子树的所有节点值小于当前节点值，右子树的所有节点值大于当前节点值。

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.

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean isValidBST(TreeNode root) {
		// Start typing your Java solution below
		// DO NOT write main() function
		return isBST(root, Integer.MIN_VALUE, Integer.MAX_VALUE);
	}
	
	public boolean isBST(TreeNode root, int min, int max){
		if(root == null)
			return true;
		if(root.val < max && root.val > min && isBST(root.left, min, root.val) && isBST(root.right, root.val, max))
			return true;
		else
			return false;
	}
}

也可用中序遍历判断是否递增数列