LeetCode 96 Unique Binary Search Trees不同的二叉搜索树的个数

 1 class Solution {
 2 public:
 3     int numTrees(int n) {
 4         int *dp = new int[n+1];
 5         for(int i=0;i<n+1;++i)
 6             dp[i] = 0;
 7             
 8         dp[0] = 1;//!!!
 9         for(int sz = 1; sz <= n; ++sz)//1-sz
10             for(int i = 1; i <= sz; ++i)//i作为root
11                 dp[sz] += dp[i-1] * dp[sz-i];
12                 
13         return dp[n];
14         
15     }
16 };