Given n, how many structurally unique BSTs (binary search trees) that store values 1...n?
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
public class Solution { /** * @paramn n: An integer * @return: An integer */ public int numTrees(int n) { // write your code here if(n <= 1) return 1; int[] dp = new int[n + 1]; dp[0] = 1; dp[1] = 1; for(int i = 2; i <= n; i++){ for(int j = 1; j <= i; j++){ dp[i] += dp[j - 1] * dp[i - j]; } } return dp[n]; } }
时间: 2024-10-08 18:23:44