3. Binary Tree Zigzag Level Order Traversal Given a binary tree, return thezigzag level ordertraversal of its nodes' values. (ie, from left to right, then right to left for the next level and alternate between). For example: Given binary tree[3,9,20,null,null,15,7], 3 / \ 9 20 ...
4.如果说左子树有n种组合,右子树有m种组合,那最终的组合数就是n*m. 把这所有的组合组装起来即可 View Code CODE: https://github.com/yuzhangcmu/LeetCode_algorithm/blob/72f914daab2fd9e2eb8a63e4643297d78d4fadaa/tree/GenerateTree2.java
Given n, how many structurally unique BST’s (binary search trees) that store values 1 … n? Example: AI检测代码解析 Input: 3 Output: 5 Explanation: 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 1. 2....
self.right = None class Solution(object): def generateTrees(self, n): """ :type n: int :rtype: List[TreeNode] """ if n == 0: return [] self.cache = {} return self._generateTrees(1, n) def _generateTrees(self, start, end): if (start, end) not in self.cache: roots = ...
初看推导公式,很容易的想到的是递归解法。我也是采用的这种方式。 为了避免重复计算,使用了map来缓存已计算过的值。 js代码如下: varnumTrees=function(n){// 预设值letmap=newMap()map.set(0,1)map.set(1,1)map.set(2,2)map.set(3,5)const result=recursive(n,map)returnresult};// 89.50%varrecursi...
Unique Binary Search Trees I: https://leetcode.com/problems/unique-binary-search-trees/description/ 解题思路: 对于n:把从1到n分别作为根节点,然后左子树*右子树,最后对其全部相加即可 class Solution { public int numTrees(int n) { int[]dp=newint[n+1];dp[0]=1;for(inti=1;i<=n;i++){for...
leetcode 96. Unique Binary Search Trees Given n, how many structurally unique BST’s (binary search trees) that store values 1 … n? Example: Input: 3 Output: 5 Explanation: Given n = 3, there are a total of 5 unique BST’s:......
class Solution(object): def generateTrees(self, n): if n == 0: return [] return self.helper(1, n) def helper(self, start, end): result = [] if start > end: result.append(None) return result for i in range(start, end + 1): # generate left and right sub tree leftTree = ...
96. Unique Binary Search Trees (DP) Givenn,howmanystructurallyuniqueBST's(binarysearchtrees)thatstorevalues1...n? Example: 分析: 参考答案解法https://leetcode.com/problems/unique-binary-search-trees/solution/ G(n)是n个数字的BST个数,注意数字 ...
* Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: vector<TreeNode*> generateTrees(int n) { ...