题目链接

https://leetcode.cn/problems/unique-binary-search-trees/description/

代码

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