题目描述

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

思路图解

class Solution:
    def numTrees(self, n: int) -> int:
        # https://leetcode-cn.com/problems/unique-binary-search-trees/solution/hua-jie-suan-fa-96-bu-tong-de-er-cha-sou-suo-shu-b/
        dp=[0]*(n+1)
        dp[0],dp[1]=1,1
        for i in range(2,n+1):
            for j in range(1,i+1):
                dp[i]+=dp[j-1]*dp[i-j]
        # print(dp)
        return dp[n]