SE_and_CS

Reverse digits of an integer.Example1: x = 123, return 321Example2: x = -123, return -321

Given an array S of n integers, are there elementsa, 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:Eleme

Given an array S of n integers, find three integers inS 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 ex

Given a sorted array, remove the duplicates in place such that each element appear onlyonce and return the new length.Do not allocate extra space for another array, you must do this in place w

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.

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:"((()))", "(()())", "(())()", "()(())", "

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.Tag：使用优先队列，时间复杂度为n*log(k)，其中n为所有元素个数，k为已排好序的链表，如果k很小的话，实现复杂度近乎为线性。#include #include #include us

Given a linked list, reverse the nodes of a linked listk 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 i

Given a linked list, swap every two adjacent nodes and return its head.For example,Given 1->2->3->4, you should return the list as 2->1->4->3.Your algorithm should use only constant spac

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.Tag：两路归并struct ListNode { int val; ListNode *nex

Implement strStr().Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.Update (2014-11-02):The signature of the function had been updat

Divide two integers without using multiplication, division and mod operator.If it is overflow, return MAX_INT.Tag: 二分求解，相当于每次除数都乘以2，注意考虑负数的情况和整数溢出的情况。int divide(int dividend, int divisor)

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

Given a digit string, return all possible letter combinations that the number could represent.A mapping of digit to letters (just like on the telephone buttons) is given below.Input:Digit

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 va

The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)P   A   H   NA P L

Implement atoi to convert a string to an integer.

Determine whether an integer is a palindrome. Do this without extra space.

Given a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.

问题：There are two sorted arrays A and B of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).

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, w

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

问题：You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it

题目：  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 leng

Given an integer, convert it to a roman numeral.Input is guaranteed to be within the range from 1 to 3999.

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

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