Here, We see Unique Binary Search Trees LeetCode Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc. with different approaches.

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Unique Binary Search Trees LeetCode Solution

Problem Statement

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

Unique Binary Search Trees Leetcode Solution C++

class Solution {
public:
    int numTrees(int n) {
        vector<int>result(n+1,0); //Initializing vector with 0
        result[1]=result[0]=1;
        for(int i=2;i<=n;i++)
        {
            for(int j=0;j<i;j++)
            {
                result[i]+=result[j]*result[i-j-1]; //Calculating C(i) to use for C(i+1) and storing it in result
            }
        }
        return result[n]; //return answer        
    }
};Code language: PHP (php)

Unique Binary Search Trees Leetcode Solution Java

class Solution {
    public int numTrees(int n) {
    int [] G = new int[n+1];
    G[0] = G[1] = 1;
    
   for(int i=2; i<=n; ++i) {
     for(int j=1; j<=i; ++j) {
       G[i] += G[j-1] * G[i-j];
     }
   }
   return G[n];    
     }
 }Code language: PHP (php)

Unique Binary Search Trees Leetcode Solution JavaScript

var numTrees = function(n) {
    let G = new Array(n+1).fill(0);
    G[0] = 1;
    G[1] = 1;
    for (let i=2;i<=n;i++) {
        for (let j=1;j<=i;j++) {
            G[i]+=G[j-1] * G[i - j];
        }
    }
    return G[n];    
};Code language: JavaScript (javascript)

Unique Binary Search Trees Leetcode Solution Python

class Solution(object):
    def numTrees(self, n):
        dp = [0 for i in range(n+1)]
        dp[0] = dp[1] = 1
    
        for i in range(2, n+1) :
            for j in range(i) :
                dp[i] += dp[j] * dp[(i-1)-j]
    
        return dp[-1]