Package g1501_1600.s1569_number_of_ways_to_reorder_array_to_get_same_bst

Class Solution

java.lang.Object
g1501_1600.s1569_number_of_ways_to_reorder_array_to_get_same_bst.Solution
public class Solution extends Object
1569 - Number of Ways to Reorder Array to Get Same BST\. Hard Given an array `nums` that represents a permutation of integers from `1` to `n`. We are going to construct a binary search tree (BST) by inserting the elements of `nums` in order into an initially empty BST. Find the number of different ways to reorder `nums` so that the constructed BST is identical to that formed from the original array `nums`. * For example, given `nums = [2,1,3]`, we will have 2 as the root, 1 as a left child, and 3 as a right child. The array `[2,3,1]` also yields the same BST but `[3,2,1]` yields a different BST. Return _the number of ways to reorder_ `nums` _such that the BST formed is identical to the original BST formed from_ `nums`. Since the answer may be very large, **return it modulo** 109 + 7. **Example 1:** ![](https://assets.leetcode.com/uploads/2020/08/12/bb.png) **Input:** nums = [2,1,3] **Output:** 1 **Explanation:** We can reorder nums to be [2,3,1] which will yield the same BST. There are no other ways to reorder nums which will yield the same BST. **Example 2:** ![](https://assets.leetcode.com/uploads/2020/08/12/ex1.png) **Input:** nums = [3,4,5,1,2] **Output:** 5 **Explanation:** The following 5 arrays will yield the same BST: [3,1,2,4,5] [3,1,4,2,5] [3,1,4,5,2] [3,4,1,2,5] [3,4,1,5,2] **Example 3:** ![](https://assets.leetcode.com/uploads/2020/08/12/ex4.png) **Input:** nums = [1,2,3] **Output:** 0 **Explanation:** There are no other orderings of nums that will yield the same BST. **Constraints:** * `1 <= nums.length <= 1000` * `1 <= nums[i] <= nums.length` * All integers in `nums` are **distinct**.

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • numOfWays

      public int numOfWays(int[] nums)