豆腐脑是咸的

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. 这道题和clone graph那道题不同的地方在于，图可以d

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

Given an array of strings, return all groups of strings that are anagrams. Note: All inputs will be in lower-case. 给定一字符串数组，返回其中是由相同字符组成只是顺序不同的字符串子数组，这些字符只出现了一次的字符串不返回。 比如 abb,bab,bba,abc 返回[

Given an array of integers, every element appears twice except for one. Find that single one. Note: Your algorithm should have a linear runtime complexity. Could you implement it without using ext

Given n points on a 2D plane, find the maximum number of points that lie on the same straight line. 用斜率算，遍历每一个点，然后以这个点和剩下的所有点连线，斜率相同的放在hash的同一位置。如果有和这个点相同的点统计下来最后算进去。 Source public int maxPoi

Given two integers representing the numerator and denominator of a fraction, return the fraction in string format. If the fractional part is repeating, enclose the repeating part in parentheses.

All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: "ACGAATTCCG". When studying DNA, it is sometimes useful to identify repeated sequences within the DNA. Wri

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. Note: Element

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. Fo

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, whe

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

Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing all ones and return its area. 设一个数组表示从第一行开始遍历的当前列的高度，再用largest rectangle in histogram那道题的方法算最大面积。 Source publ

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 fille