LeetCode--Validate Binary Search Tree(驗證二叉搜尋樹)C++
阿新 • • 發佈:2018-12-24
題目描述: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.
題目翻譯:
給定一個二叉樹,確定它是否是一個有效的二叉查詢樹(BST)。
假定一個BST的定義如下:
一個節點的左子樹只包含值小於該節點值的節點。
一個節點的右子樹只包含值大於該節點值的節點。
左子樹和右子樹也必須是二叉查詢樹。
思路分析,本題我們使用遞迴的思,程式碼實現如下:
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
bool isValidBST(TreeNode *root)
{
return isValid(root,INT_MIN,INT_MAX);
}
bool isValid(TreeNode* root,int min,int max)
{
if(root == NULL)
return true;
return root->val > min && root->val < max &&
isValid(root->left,min,root->val ) &&
isValid(root->right,root->val,max);
}
};