leetcode Unique Binary Search Trees

Description:

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

Solution:

int numTrees(int n) {    int dp[n+1];    dp[0] = dp[1] = 1;    for (int i=2; i<=n; i++) {        dp[i] = 0;        for (int j=1; j<=i; j++) {            dp[i] += dp[j-1] * dp[i-j];        }    }    return dp[n];}