163题 Unique Binary Search Trees

Unique Binary Search Trees

Description
Given n, how many structurally unique BSTs (binary search trees) that store values 1…n?

public class Solution {
    /**
     * @param n: An integer
     * @return: An integer
     */
    public int numTrees(int n) {
        // write your code here、
        if(n == 0 ||n == 1){
            return 1;
        }
         
         
    int[] C = new int[n+1];
    C[0] = 1;
    for(int num=1;num<=n;num++){  
        for(int i=0;i<=num-1;i++){  
           C[num] += C[i]*C[(num-1)-i];  
       }  
    }
       return C[n];
    }
}