096 Unique Binary Search Trees

这道题目就是catalan数，因为递归关系为

代码为

class Solution:
    # @param {integer} n
    # @return {integer}
    def numTrees(self, n):
        # Catalan Number
        ans = 1
        for i in range(1, n+1):
            ans *= (n+i)*1.0/i
        return int(round(ans/(n+1)))

时间： 2024-10-29 19:07:54

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