[动态规划] leetcode 96 Unique Binary Search Trees

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

        左子树个数 * 右子树个数

class Solution {
public:
    int numTrees(int n) {
        vector<int> dp(n + 1);
        dp[1] = 1;
        for(int i = 2;i <= n;i++)
        {
            dp[i] = dp[i - 1] + dp[i - 1];
            for(int j = 1;j <= i - 1; j++)
            {
                dp[i] += dp[j] * dp[i - 1 - j];
            }
        }
        return dp[n];
    }
};