[LeetCode]96. Unique Binary Search Trees

https://leetcode.com/problems/unique-binary-search-trees/

public class Solution {
    public int numTrees(int n) {
        int[] dp = new int[n + 1];
        dp[0] = 1;
        dp[1] = 1;
        for (int i = 2; i <=n; i++) {
            for (int j = 1; j <= i; j++) {
                // 当往原有的树中插入一个更大的node时，实际插入位置将原有的树分成node数为j - 1和i - j的两个部分
                dp[i] += (dp[j - 1] * dp[i - j]);
            }
        }
        return dp[n];
    }
}