chfe910的专栏

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 exampl

Write a function to find the longest common prefix string amongst an array of strings.这个题目非常简单，只要弄清楚题意就可以非常快地解决，我的C++代码实现如下： string longestCommonPrefix(vector<string> &strs) { if (strs.empt

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. - push(x) – Push element x onto stack. - pop() – Removes the element on top of the stack. - to

Validate if a given string is numeric. Some examples: "0" => true " 0.1 " => true "abc" => false "1 a" => false "2e10" => true Note: It is intended for the problem statement to be

Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999.欲了解罗马数字的拼写规则请参考：http://blog.youkuaiyun.com/chfe007/article/details/44037079C++代码实现如下： string

Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.这个题目首先要了解罗马数字的拼写规则（以下引自维基百科）：罗马数字共有7个，即I（1）、V（5）、X（10）、L（50）、C（100）、D（500）和M（1000）。按照下述的规则

Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST. Calling next() will return the next smallest number in the BST. Note: next()

Given a 2D board containing ‘X’ and ‘O’, capture all regions surrounded by ‘X’. A region is captured by flipping all ‘O’s into ‘X’s in that surrounded region. For example, X X X X X O O X

Given an unsorted array of integers, find the length of the longest consecutive elements sequence. For example, Given [100, 4, 200, 1, 3, 2], The longest consecutive elements sequence is [1, 2

LeetCode[Sort]: Largest Number Given a list of non negative integers, arrange them such that they form the largest number. For example, given [3, 30, 34, 5, 9], the largest formed number is 953433

Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is.

Given an array and a value, remove all instances of that value in place and return the new length.The order of elements can be changed. It doesn't matter what you leave beyond the new length.方

Given a non-negative number represented as an array of digits, plus one to the number.The digits are stored such that the most significant digit is at the head of the list.一开始我误解了题目的意思，以为是新建一个

Given two sorted integer arrays A and B, merge B into A as one sorted array.Note:You may assume that A has enough space (size that is greater or equal to m + n) to hold additional elements from B.

Given numRows, generate the first numRows of Pascal's triangle.For example, given numRows = 5,Return[ [1], [1,1], [1,2,1], [1,3,3,1], [1,4,6,4,1]]这个问题比较简单，大家的解法大同小异。时间复杂度都

Given a list, rotate the list to the right by k places, where k is non-negative.For example:Given 1->2->3->4->5->NULL and k = 2,return 4->5->1->2->3->NULL.看到这个题目感到奇怪的是为什么是“右旋”，而不是“左旋

A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.Return a deep copy of the list./** * Definition for singly-linke

Given a linked list, remove the nth node from the end of list and return its head.For example,Given linked list: 1->2->3->4->5, and n = 2.After removing the second node from the end, the linked

Reverse a linked list from position m to n. Do it in-place and in one-pass.For example:Given 1->2->3->4->5->NULL, m = 2 and n = 4,return 1->4->3->2->5->NULL.Note:Given m, n satisfy the f

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.For example,Given 1->2->3->3->4->4->5, return 1->2->5.Given 1

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.The brackets must close in the correct order, "()" and "()[]{}" are all valid bu

Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word in the string.If the last word does not exist, return 0.Note: A word is defin

Suppose a sorted array is rotated at some pivot unknown to you beforehand.(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).Find the minimum element.You may assume no duplicate exists in the

Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.You should preserve the original relative order of the nodes in each of t

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.The Sudoku board could be partially filled, where empty cells are filled with the character '.'.A partially filled su

Given an array of integers, find two numbers such that they add up to a specific target number.The function twoSum should return indices of the two numbers such that they add up to the target, where

Given an array of strings, return all groups of strings that are anagrams.Note: All inputs will be in lower-case.思路：对每一个单词的所有字母按照字典顺序排序，排序结果作为key，所有具有相同key的单词组合在一起成为一个Anagram group。最后返回所有的Anag

Given an index k, return the kth row of the Pascal's triangle.For example, given k = 3,Return [1,3,3,1].Note:Could you optimize your algorithm to use only O(k) extra space?这个问题比较简单。v

Given a linked list, determine if it has a cycle in it.Follow up:Can you solve it without using extra space?这个题目如果没有空间复杂度O(1)的限制，我可以想到的方法就是：遍历整个list，将每个节点的地址存入一个vector，如果发现某个节点的next的地址已经在vec

Given a linked list, return the node where the cycle begins. If there is no cycle, return null.Follow up:Can you solve it without using extra space?这个题目跟Linked List Cycle一样，我也没有能够自己独立找到解决方法，

Given two binary strings, return their sum (also a binary string).For example,a = "11"b = "1"Return "100".我的C++实现代码如下：string addBinary(string a, string b) { string sum; int c

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).Recursive Algorithmclass Solution {public: bool isSymmetric(TreeNode *root) { return

Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).这个题目比较简单，借助容器queue即可完成二叉树的层序遍历。我的C++实现代码如下：vector > levelOrder(TreeNode *

Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).这个简单的问题可以这样解决：利用LeetCode[Tree]: Binary Tree Level

Write a program to find the node at which the intersection of two singly linked lists begins.Notes:If the two linked lists have no intersection at all, return null.The linked lists must retain t

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.Follow up:Did you use extra space?A straight forward solution using O(mn) space is probably a bad ide

Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:Integers in each row are sorted from left to right.The first integer of each row

Given a binary treestruct TreeLinkNode {TreeLinkNode left;TreeLinkNode right;TreeLinkNode next;}Populate each next pointer to point to its next right node. If there is no next right node,

Given a binary tree, return the inorder traversal of its nodes' values.For example:Given binary tree {1,#,2,3},1\2/3return [1,3,2].这个题目的递归算法很简单：class Solution {public: v

Given a binary tree, flatten it to a linked list in-place.For example,Given1/ \2 5/ \ \3 4 6The flattened tree should look like:1\2\3\4\5\6递归算法这种问题非常适合用