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

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;}};