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.<p>Hard</p> <p>Given an array <code>nums</code> that represents a permutation of integers from <code>1</code> to <code>n</code>. We are going to construct a binary search tree (BST) by inserting the elements of <code>nums</code> in order into an initially empty BST. Find the number of different ways to reorder <code>nums</code> so that the constructed BST is identical to that formed from the original array <code>nums</code>.</p> <ul> <li>For example, given <code>nums = [2,1,3]</code>, we will have 2 as the root, 1 as a left child, and 3 as a right child. The array <code>[2,3,1]</code> also yields the same BST but <code>[3,2,1]</code> yields a different BST.</li> </ul> <p>Return <em>the number of ways to reorder</em> <code>nums</code> <em>such that the BST formed is identical to the original BST formed from</em> <code>nums</code>.</p> <p>Since the answer may be very large, <strong>return it modulo</strong> <code>10<sup>9</sup> + 7</code>.</p> <p><strong>Example 1:</strong></p> <p><img src="https://assets.leetcode.com/uploads/2020/08/12/bb.png" alt="" /></p> <p><strong>Input:</strong> nums = [2,1,3]</p> <p><strong>Output:</strong> 1</p> <p><strong>Explanation:</strong> 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.</p> <p><strong>Example 2:</strong></p> <p><img src="https://assets.leetcode.com/uploads/2020/08/12/ex1.png" alt="" /></p> <p><strong>Input:</strong> nums = [3,4,5,1,2]</p> <p><strong>Output:</strong> 5</p> <p><strong>Explanation:</strong> The following 5 arrays will yield the same BST:</p> <pre><code> [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] </code></pre> <p><strong>Example 3:</strong></p> <p><img src="https://assets.leetcode.com/uploads/2020/08/12/ex4.png" alt="" /></p> <p><strong>Input:</strong> nums = [1,2,3]</p> <p><strong>Output:</strong> 0</p> <p><strong>Explanation:</strong> There are no other orderings of nums that will yield the same BST.</p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= nums.length <= 1000</code></li> <li><code>1 <= nums[i] <= nums.length</code></li> <li>All integers in <code>nums</code> are <strong>distinct</strong>.</li> </ul>

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • numOfWays

      public int numOfWays(int[] nums)