Unique Binary Search Trees Leetcode Solution

In this post, we are going to solve the Unique Binary Search Trees Leetcode Solution problem of Leetcode. This Leetcode problem is done in many programming languages like C++, Java, and Python.

Table of Contents

Problem

Given an integer n, return the number of structurally unique BST’s (binary search trees) which has exactly n nodes of unique values from 1 to n.

Example 1:

Input: n = 3
Output: 5

Example 2:

Input: n = 1
Output: 1

Constraints:

1 <= n <= 19

Now, let’s see the leetcode solution of Unique Binary Search Trees Leetcode Solution.

Unique Binary Search Trees Leetcode Solution in Python

class Solution:
  def numTrees(self, n: int) -> int:
    # G[i] := # Of unique BST's that store values 1..i
    G = [1, 1] + [0] * (n - 1)

    for i in range(2, n + 1):
      for j in range(i):
        G[i] += G[j] * G[i - j - 1]

    return G[n]

Unique Binary Search Trees Leetcode Solution in CPP

class Solution {
 public:
  int numTrees(int n) {
    // G[i] := # of unique BST's that store values 1..i
    vector<int> G(n + 1);
    G[0] = 1;
    G[1] = 1;

    for (int i = 2; i <= n; ++i)
      for (int j = 0; j < i; ++j)
        G[i] += G[j] * G[i - j - 1];

    return G[n];
  }
};

Unique Binary Search Trees Leetcode Solution in Java

class Solution {
  public int numTrees(int n) {
    // G[i] := # of unique BST's that store values 1..i
    int[] G = new int[n + 1];
    G[0] = 1;
    G[1] = 1;

    for (int i = 2; i <= n; ++i)
      for (int j = 0; j < i; ++j)
        G[i] += G[j] * G[i - j - 1];

    return G[n];
  }
}

Note: This problem Unique Binary Search Trees is generated by Leetcode but the solution is provided by Chase2learn This tutorial is only for Educational and Learning purposes.

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