96. Unique Binary Search Trees

Given n, how many structurally unique BST’s (binary search trees) that store values 1…n?

For example,
Given n = 3, there are a total of 5 unique BST’s.

   1         3     3      2      1    \       /     /      / \      \     3     2     1      1   3      2    /     /       \                 \   2     1         2                 3

class Solution {        public int numTrees(int n) {        int[] count = new int[n + 2];        count[0] = 1;        count[1] = 1;        for(int i = 2; i <= n; i++){            for(int j = 0; j < i; j++){                count[i] += count[j] * count[i - j - 1];            }        }        return count[n];    }}