【LeedCode】96. Unique Binary Search Trees

Description:

Given n, how many structurally unique BST's (binary search trees) that store values 1...n?

For example,
Given n = 3, there are a total of 5 unique BST's.

   1         3     3      2      1    \       /     /      / \      \     3     2     1      1   3      2    /     /       \                 \   2     1         2                 3

Solutions:

class Solution {

public:

    int numTrees(int n) {

        int *G=new int[n+1]();

        G[0]=1;

        G[1]=1;

        for(int i=2;i<=n;i++)

        {

            for(int j=0;j<i;j++)

                G[i]+=G[j]*G[i-j-1];

        }

        return G[n];

    }

};