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31 lines (26 loc) · 820 Bytes
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ValidateBST.cpp
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31 lines (26 loc) · 820 Bytes
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struct TreeNode {
int val;
TreeNode* left;
TreeNode* right;
TreeNode() : val(0), left(nullptr), right(nullptr) {}
TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
TreeNode(int x, TreeNode* left, TreeNode* right) : val(x), left(left), right(right) {}
};
class Solution {
public:
bool isValidBST(TreeNode* root) {
return validate(root, nullptr, nullptr);
}
bool validate(TreeNode* root, TreeNode* low, TreeNode* high) {
if (root == nullptr) {
return true;
}
if (low != nullptr && root->val <= low->val) {
return false;
}
if (high != nullptr && root->val >= high->val) {
return false;
}
return validate(root->left, low, root) && validate(root->right, root, high);
}
};