LeetCode OJ——Unique Binary Search Trees

class Solution {
public:
    int numTrees(int n) {
        if(!n||n==)return ;

        vector<int> numVector;
        numVector.assign(n+,);
        numVector[]=;
        numVector[]=;

        for(int i=;i<=n;++i)
        {
            for(int j=;j<=i-;++j)
            {
                numVector[i]+=numVector[j]*numVector[i--j];
            }
        }

        return numVector[n];
    }
};