Given a list, rotate the list to the right by k places, where k is non-negative.   Example Given 1->2->3->4->5 and k = 2, return 4->5->1->2->3. 解法一: public class Solution { private int getLength(ListNode head) { int length = 0; whi…

2. Add Two Numbers[medium] You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list. You…

92. Reverse Linked List II[Medium] 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 fo…

82. Remove Duplicates from Sorted List II[Medium] 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…

189. Rotate Array[easy] Rotate an array of n elements to the right by k steps. For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4]. Note:Try to come up as many solutions as you can, there are at least 3 differen…

61. Search for a Range[medium] Given a sorted array of n integers, find the starting and ending position of a given target value. If the target is not found in the array, return [-1, -1]. Have you met this question in a real interview? Yes Example Gi…

62. Search in Rotated Sorted Array[medium] 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). You are given a target value to search. If found in the array return its index, ot…

74. First Bad Version [medium] The code base version is an integer start from 1 to n. One day, someone committed a bad version in the code case, so it caused this version and the following versions are all failed in the unit tests. Find the first bad…

75. Find Peak Element [medium] There is an integer array which has the following features: The numbers in adjacent positions are different. A[0] < A[1] && A[A.length - 2] > A[A.length - 1]. We define a position P is a peek if: A[P] > A[P-…

159. Find Minimum in Rotated Sorted Array [medium] 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. Notice You may assume no duplicate exists in the…

There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1] Given the total number of courses and a l…

Given a binary tree, flatten it to a linked list in-place. For example, given the following tree: 1 / \ 2 5 / \ \ 3 4 6 The flattened tree should look like: 1 \ 2 \ 3 \ 4 \ 5 \ 6 Accepted 218,918 Submissions 533,947 [解析]由上图可知,如果右子树不为空,则右子树最后肯定为左子树最有一…

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. 解题思路: 题目看上去很简单,但是需要注意一下点: 1.任何输入都有可能,即使是无效的输入(例如链表为空,k不为0),所以程序开始时的检…

You are given an n x n 2D matrix representing an image. Rotate the image by 90 degrees (clockwise). Follow up:Could you do this in-place? 解题思路1,时间复杂度o(n): 顺时针旋转的规律很好找到,为了完全在矩阵内部操作,普通的办法就是每遍历到一个位置,则将与这个位置相关的一周(旋转一周涉及到的4个位置)都进行替换操作. 代码: class Solution…

Given a string s, partition s such that every substring of the partition is a palindrome. Return all possible palindrome partitioning of s. For example, given s = "aab", Return [ ["aa","b"], ["a","a","…

A message containing letters from A-Z is being encoded to numbers using the following mapping: 'A' -> 1 'B' -> 2 ... 'Z' -> 26 Given an encoded message containing digits, determine the total number of ways to decode it. For example,Given encoded…

Given a 2D board and a word, find if the word exists in the grid. The word can be constructed from letters of sequentially adjacent cell, where "adjacent" cells are those horizontally or vertically neighboring. The same letter cell may not be us…

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place. 解题思路: 题目乍一看很简单,将矩阵当前为0的位的行列都置为0: 问题在于:当遇到一个已知0时,不能立刻将其行列置0,因为这样会把原本不是0的位更改,导致继续遍历的时候无法区分哪些是初始0,哪些是后改0: 有一个解决方法,就是先遍历所有位,记录所有初始为0的行列坐标,遍历一遍之后,再统一做更改: 但是这个解决方…

Implement pow(x, n). 解题思路: 求浮点数的幂次方,注意可能为负数次幂: 可以使用二分搜索的思想,当n为偶数时,x^n = x^(n/2) * x^(n/2),因此只需要求得一半的幂次方,将结果平方,就得到所求结果. 解题步骤: 1.递归最底层,n == 0 时,返回1: 2.求出t = pow(x, n/2): 3.判断n的奇偶性: a. 如果奇数,要判断n的符号,n为负数乘以1/x,n为正数时乘以x: b. 如果偶数,不需要多乘:同时,也不需要判断符号,因为符号形式已经包…

Given an array of strings, group anagrams together. For example, given: ["eat", "tea", "tan", "ate", "nat", "bat"], Return: [ ["ate", "eat","tea"], ["nat",…

There are two sorted arrays nums1 and nums2 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)). You may assume nums1 and nums2 cannot be both empty. Example 1: nums1 = [1, 3]…

Given an array equations of strings that represent relationships between variables, each string equations[i] has length 4 and takes one of two different forms: "a==b" or "a!=b".  Here, a and b are lowercase letters (not necessarily dif…

求集合不重复的子集: 下面python的写法很好啊! class Solution(object): def subsets(self, nums): """ :type nums: List[int] :rtype: List[List[int]] """ res = [[]] for num in nums : for temp in res[:] : x = temp[:] x.append(num) res.append(x) retur…

因为要考虑超时问题,所以虽然简单的for循环也可以做,但是要用map等内部红黑树实现的容器. Given an array of integers, find out whether there are two distinct indices i and j in the array such that the absolute difference between nums[i] and nums[j] is at most t and the absolute difference bet…

Implement pow(x, n). Notice You don't need to care about the precision of your answer, it's acceptable if the expected answer and your answer 's difference is smaller than 1e-3.   Example Pow(2.1, 3) = 9.261 Pow(0, 1) = 0 Pow(1, 0) = 1 Challenge O(lo…

Say you have an array for which the ith element is the price of a given stock on day i. If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock), design an algorithm to find the maximum profit.   Ex…

Given k strings, find the longest common prefix (LCP).   Example For strings "ABCD", "ABEF" and "ACEF", the LCP is "A" For strings "ABCDEFG", "ABCEFG" and "ABCEFA", the LCP is "ABC…

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. Notice Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c) The solu…

Given an absolute path for a file (Unix-style), simplify it. For example,path = "/home/", => "/home"path = "/a/./b/../../c/", => "/c" Corner Cases: Did you consider the case where path = "/../"?In th…

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 as a linked list. Input: (2 -> 4 -> 3) + (5 -> 6 ->…