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
class Solution { public: int numTrees(int n) { int result[n+1]; for(int i=0;i<=n;++i)result[i] = 0; result[0] = 1; result[1] = 1; for(int i=2;i<=n;++i) { for(int j=1;j<=i;++j) { result[i] += result[j-1]*result[i-j]; } } return result[n]; } };
LeetCode Unique Binary Search Trees
原文：http://www.cnblogs.com/55open/p/4192468.html