Tomcat的专栏

从今天开始进行leetcode之旅。古语有云“学以致用”，尤其适合于coding，因为很多时候都是学会了不一定会用，会用了不一定知道在哪用。而算法与数据结构又是coding的核心，更是面试的重灾区。leetcode是一个非常好的深入enhance算法与数据结构的地方，我们不能单纯为了面试而刷题，这并不利于职业发展；但也不能不有所准备，面试又有其独有的特点。面试并不同于平常编程，有IDE有Google

Next Permutation

[LeetCode]ZigZag Conversion

[LeetCode]Longest Substring Without Repeating Characters

这道题目本身并不难，难点在于它是我做的第一道。在此我建议大家做leetecode最好不要用IDE，从实际出发考察自己。

第二题

Search in Rotated Sorted Array

Search for a Range

[LeetCode]Reverse Integer

Search Insert Position

3Sum

Count and Say

Group Anagrams

Jump Game II

N-Queens

Question Follow up for N-Queens problem.Now, instead outputting board configurations, return the total number of distinct solutions.本题难度Hard。 【思路】 N-Queens中返回棋盘变成了解的个数。不必多说。【代码】public class Solution

Question 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 verti

Question Given two integers n and k, return all possible combinations of k numbers out of 1 … n.For example, If n = 4 and k = 2, a solution is:[ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4],

Question Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue.Here, we will use the inte

Letter Combinations of a Phone Number

Question Find the contiguous subarray within an array (containing at least one number) which has the largest sum.For example, given the array [-2,1,-3,4,-1,2,1,-5,4], the contiguous subarray [4,-1,2,

Question Given an array of non-negative integers, you are initially positioned at the first index of the array.Each element in the array represents your maximum jump length at that position.Determine

Combination Sum

Combination Sum II

Question Given a set of distinct integers, nums, return all possible subsets.Note: The solution set must not contain duplicate subsets.For example, If nums = [1,2,3], a solution is:[ [3], [1],

QuestionGiven an absolute path for a file (Unix-style), simplify it.For example, path = “/home/”, => “/home” path = “/a/./b/../../c/”, => “/c”本题难度Medium。【复杂度】 时间 O(N) 空间 O(N) 【思路】 思路很简单，先将整个路径按照/

QuestionFollow up for “Remove Duplicates”: What if duplicates are allowed at most twice?For example, Given sorted array nums = [1,1,1,2,2,3],Your function should return length = 5, with the first fiv

Remove Nth Node From End of List

Longest Valid Parentheses

Question Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.For example, Given the following matrix:[ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ]]Yo

Question本题难度Hard。排序+双指针【复杂度】 时间 O(Nlog(N)) 空间 O(N) 【思路】 先按照每个元素的start从小到大进行排序。然后利用双指针法，设置区间(low,high)，如果新的元素i的start要大于high，说明(low,high)没有overlap，就将(low,high)放入结果中，然后将双指针移动：low=i.start;high=i.end;否

Question Follow up for “Search in Rotated Sorted Array”: What if duplicates are allowed?Would this affect the run-time complexity? How and why?Write a function to determine if a given target is in th

Question 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

Question Given a sorted linked list, delete all duplicates such that each element appear only once.For example, Given 1->1->2, return 1->2. Given 1->1->2->3->3, return 1->2->3.Subscribe to see which

Question: 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.本题难度easy，关键在于别想复杂了。题目是有assumption的：sort都是从小到大。

Generate Parentheses

Question Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).You may assume that the intervals were initially sorted according to their start times.

Question 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

Question: Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.本题难度为hard。

Question Delete a node in a BST.Basically, the deletion can be divided into two stages:Search for a node to remove. If the node is found, delete the node. Example:root = [5,3,6,2,4,null,7]key = 3