LeetCode刷题实战96：不同的二叉搜索树
算法的重要性，我就不多说了吧，想去大厂，就必须要经过基础知识和业务逻辑面试+算法面试。所以，为了提高大家的算法能力，这个公众号后续每天带大家做一道算法题，题目就从LeetCode上面选 ！
今天和大家聊的问题叫做 不同的二叉搜索树，我们先来看题面：
https://leetcode-cn.com/problems/unique-binary-search-trees/
Given n, how many structurally unique BST's (binary search trees) that store values 1 ... n?
题意
解题
class Solution {
public int numTrees(int n) {
if (n == 0 || n == 1) return 1;
int res = 0;
for (int i = 1; i <= n; i++) {
res += numTrees(i - 1) * numTrees(n - i);
}
return res;
}
}
public class Solution {
public int numTrees(int n) {
int[] dp = new int[n + 1];
dp[0] = 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];
}
}
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