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Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses. For example, given n = 3, a solution set is: "((()))", "(()())", "(())()", "()(())", "()()

一道非常有意思的题目。 原题如下： Given a set of distinct integers, S, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example, If S = [1,2,3], a solution is: [ [3], [

原题如下; Given inorder and postorder traversal of a tree, construct the binary tree. Note: You may assume that duplicates do not exist in the tree. 题意很简单：根据中序遍历和后序遍历的序列生成树 思路很简单：根据后序遍历的序列确定根节点，在中序遍历中找到根节点，将原来的序列分为左右两个部分，递归解决左右两个部分就可以解决这个问题。 Java代码如下： publ

这道题承接Unique Binary Search Trees，只需要返回搜索二叉树的个数，用DP求解。但是这道题需要得到所有树的集合，可以用DFS求解。 原题是这个样子的： Given n, generate all structurally unique BST's (binary search trees) that store values 1...n. For example, Given n = 3, your program should return all 5 unique BST's

public TreeNode sortedListToBST(ListNode head) { if (head == null) return null; int len = 0; ListNode nextNode = head; while (nextNode != null) { nextNode = nextNode.next; len++; } return buildTree(head, 0, len - 1); } public Tree

Given two words word1 and word2, find the minimum number of steps required to convert word1 to word2. (each operation is counted as 1 step.) You have the following 3 operations permitted on a word: a) Insert a character b) Delete a character c) Replace a

终于完成了LeetCode 上AC率在30%以上的题目，这道题是最后一道，纪念一下。 原题是这个样子的： Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number. An example is the root-to-leaf