LeetCode 刷题【96. 不同的二叉搜索树】

96. 不同的二叉搜索树

自己做

解：回溯统计

class Solution {
public:int searchTrees(int begin, int end){if(begin >= end)         //构不成树了return 1;int res = 0;for(int i = begin; i <= end; i++){              //当前结点选取//划分左右子树int left = searchTrees(begin, i - 1);       //左子树部分int right = searchTrees(i + 1, end);        //右子树部分res += left * right;}return res;}int numTrees(int n) {return searchTrees(1, n);}
}; 

看题解

动态规划

官方代码如下

class Solution {
public:int numTrees(int n) {vector<int> G(n + 1, 0);G[0] = 1;G[1] = 1;for (int i = 2; i <= n; ++i) {for (int j = 1; j <= i; ++j) {G[i] += G[j - 1] * G[i - j];}}return G[n];}
};