[LeetCode 98]Validate Binary Search Tree

题目链接：validate-binary-search-tree

//验证是否为二叉排序树/** * 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. * */public class ValidateBinarySearchTree {public class TreeNode {int val;TreeNode left;TreeNode right;TreeNode(int x) {val = x;}}//74 / 74 test cases passed.//Status: Accepted//Runtime: 292 ms//Submitted: 0 minutes agopublic boolean isValidBST(TreeNode root) {return isValidBST(root, Integer.MIN_VALUE, Integer.MAX_VALUE);}public boolean isValidBST(TreeNode root, int min, int max) {if(root == null) return true;boolean l = true;boolean r = true;if(root.val >= min && root.val <= max) {//min <= root.val <= maxif(root.val != Integer.MIN_VALUE)l = isValidBST(root.left, min, root.val – 1);else {// 当root.val = Integer.MIN_VALUE时if(root.left != null) l = false;//如果还有左节点，则不是二叉排序树}if(root.val != Integer.MAX_VALUE)r = isValidBST(root.right, root.val + 1, max);else {// 当root.val = Integer.MAX_VALUE时if(root.right != null) l = false;//如果还有右节点，，则不是二叉排序树}return l && r;}else return false;}public static void main(String[] args) {// TODO Auto-generated method stub}}

告诉自己，我这次失败了，重新开始吧!下次我会吸取教训，不让自己犯同样的错误的