Leetcode 255. Verify Preorder Sequence in Binary Search Tree (Medium) (cpp)

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本文介绍了一个中等难度的LeetCode题目：验证一个整数序列是否为二叉搜索树的正确前序遍历序列。文章提供了一种使用递归方法的C++解决方案，并考虑了每个节点的值相对于父节点的大小限制。

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Leetcode 255. Verify Preorder Sequence in Binary Search Tree (Medium) (cpp)

Tag: Tree, Stack

Difficulty: Medium

/*

255. Verify Preorder Sequence in Binary Search Tree (Medium)

Given an array of numbers, verify whether it is the correct preorder traversal sequence of a binary search tree.

You may assume each number in the sequence is unique.

Follow up:
Could you do it using only constant space complexity?

*/
class Solution {
public:
	bool verifyPreorder(vector<int>& preorder) {
		int i = 0;
		verifyPreorder(preorder, i, INT_MIN, INT_MAX);
		return i >= preorder.size() ? true : false;
	}
private:
	void verifyPreorder(vector<int>& nums, int& i, int low, int high) {
		if (i >= nums.size() || nums[i] > high || nums[i] < low) return;
		int cur = nums[i++];
		verifyPreorder(nums, i, low, cur);
		verifyPreorder(nums, i, cur, high);
		return;
	}
};