Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The count-and-say sequence is the sequence of integers beginning as follows:1, 11, 21, 1211, 111221, ...

1. 题目 Write a program to solve a Sudoku puzzle by filling the empty cells. Empty cells are indicated by the character '.'. You may assume that there will be only one unique solution. A sudoku puzzle... ...and its solution numbers marked in red. [链接] 2. 思路 每次找到最合适填入点进行试探。每次...

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.

Given a sorted array of integers, find the starting and ending position of a given target value.

Suppose a sorted array is rotated at some pivot unknown to you beforehand.

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.

You are given a string, s, and a list of words, words, that are all of the same length. Find all starting indices of substring(s) in s that is a concatenation of each word in words exactly once and without any intervening characters.

Divide two integers without using multiplication, division and mod operator.

Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Given an array and a value, remove all instances of that value in place and return the new length.

Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.

Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.

Given a linked list, swap every two adjacent nodes and return its head.

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

Given a linked list, remove the nth node from the end of list and return its head.

Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.

Given a digit string, return all possible letter combinations that the number could represent.

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Write a function to find the longest common prefix string amongst an array of strings.

1. 题目 Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999. 2. 思路 按序累加即可。考虑{4、9}*10^i的场景，做好减法和多跳一步。 3. 代码 耗时：29ms {代码...}

1. 题目 Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. 2. 思路 罗马数字的规则： 字符：M=1000, D=500, C=100， L=50， X=10， V=5， I=1. 按序累加即可。 {1,5} * 10^i， 在千这个范围的规则字符数 考虑字符的下一位的最小值，比如{4,9}*10^i， 是通...

Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a container, such that the container contains the most wa...

'.' Matches any single character.'*' Matches zero or more of the preceding element.