Leetcode: Validate Binary Search Tree

思路:

1. 难点在于构造递归函数的参数

2. 参数要包含上下界, 才能具有全局性. 第一次提交 WA 了, 因为写成来的判断函数是局部性的

代码:

const int POS = 1E9;
const int NEG = -1E9;
class Solution {
public:bool ans;bool isValidBST(TreeNode *root) {if(root == NULL)return true;ans = true;if(root->left) isBST(root->left, NEG, root->val);if(root->right)isBST(root->right, root->val, POS);return ans;}void isBST(TreeNode *root, const int &minval, const int &maxval) {if(root->val >= maxval || root->val <= minval)ans = false;if(root->left && ans) {isBST(root->left, minval, root->val);}if(root->right && ans)isBST(root->right, root->val, maxval);}
};

转载于:https://www.cnblogs.com/xinsheng/p/3468240.html

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