【Leetcode】Unique Binary Search Trees

题目链接：https://leetcode.com/problems/unique-binary-search-trees/

题目：

BST's

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

思路：

看到题目半天没思路。。看了别人的题解才反应过来。。参考博文：点击打开链接

算法：

 
     
  
1. public int numTrees(int n) {  
2. int f[] = new int[n + 1];  
3. 0] = 1;  
4. for (int i = 1; i <= n; i++) {  
5. for (int j = 0; j < i; j++)  
6. 1 - j];  
7.     }  
8. return f[n];  
9. }