James Pan

原题网址：https://leetcode.com/problems/serialize-and-deserialize-bst/Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file

原题网址：https://leetcode.com/problems/the-skyline-problem/A city's skyline is the outer contour of the silhouette formed by all the buildings in that city when viewed from a distance. Now suppose y

原题网址：https://leetcode.com/problems/reconstruct-itinerary/Given a list of airline tickets represented by pairs of departure and arrival airports [from, to], reconstruct the itinerary in order.

原题网址：https://leetcode.com/problems/design-twitter/Design a simplified version of Twitter where users can post tweets, follow/unfollow another user and is able to see the 10 most recent tweets in

原题网址：https://leetcode.com/problems/wiggle-sort-ii/Given an unsorted array nums, reorder it such that nums[0] nums[2] .Example:(1) Given nums = [1, 5, 1, 1, 6, 4], one possible answer is

原题网址：https://leetcode.com/problems/subsets-ii/Given a collection of integers that might contain duplicates, nums, return all possible subsets.Note:Elements in a subset must be in non-d

原题网址：https://leetcode.com/problems/merge-sorted-array/Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.Note:You may assume that nums1 has enough

原题网址：https://leetcode.com/problems/partition-list/Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.You should pres

原题网址：https://leetcode.com/problems/search-in-rotated-sorted-array-ii/Follow up for "Search in Rotated Sorted Array":What if duplicates are allowed?Would this affect the run-time complexity

原题网址：https://leetcode.com/problems/maximum-gap/Given an unsorted array, find the maximum difference between the successive elements in its sorted form.Try to solve it in linear time/space.

原题网址：https://leetcode.com/problems/h-index-ii/Follow up for H-Index: What if the citations array is sorted in ascending order? Could you optimize your algorithm?Hint:Expected runtime c

原题网址：https://leetcode.com/problems/minimum-moves-to-equal-array-elements-ii/Given a non-empty integer array, find the minimum number of moves required to make all array elements equal, where a m

原题网址：https://leetcode.com/problems/heaters/Winter is coming! Your first job during the contest is to design a standard heater with fixed warm radius to warm all the houses.Now, you are given

原题网址：https://leetcode.com/problems/minimum-number-of-arrows-to-burst-balloons/There are a number of spherical balloons spread in two-dimensional space. For each balloon, provided input is the st

原题网址：https://leetcode.com/problems/assign-cookies/Assume you are an awesome parent and want to give your children some cookies. But, you should give each child at most one cookie. Each child i h

原题网址：https://leetcode.com/problems/largest-divisible-subset/Given a set of distinct positive integers, find the largest subset such that every pair (Si, Sj) of elements in this subset satisfie

原题网址：https://leetcode.com/problems/find-k-pairs-with-smallest-sums/You are given two integer arrays nums1 and nums2 sorted in ascending order and an integer k.Define a pair (u,v) which consists

原题网址：https://leetcode.com/problems/count-of-smaller-numbers-after-self/You are given an integer array nums and you have to return a new counts array. The counts array has the property where coun

原题网址:https://leetcode.com/problems/rearrange-string-k-distance-apart/Given a non-empty string str and an integer k, rearrange the string such that the same characters are at least distance k fro

原题网址：https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/Follow up for "Remove Duplicates":What if duplicates are allowed at most twice?For example,Given sorted array nu

原题网址：https://leetcode.com/problems/search-a-2d-matrix/Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:Integers in each

原题网址：https://leetcode.com/problems/sort-colors/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 re

原题网址：https://leetcode.com/problems/sort-list/Sort a linked list in O(n log n) time using constant space complexity.方法一：分区排序，以第一个元素为参照，分为大中小。/** * Definition for singly-linked list. * publi

原题网址：https://leetcode.com/problems/wiggle-sort-ii/Given an unsorted array nums, reorder it such that nums[0] nums[2] .Example:(1) Given nums = [1, 5, 1, 1, 6, 4], one possible answer is

原题网址：https://leetcode.com/problems/insertion-sort-list/Sort a linked list using insertion sort.方法：/** * Definition for singly-linked list. * public class ListNode { * int val; * Li

原题网址：https://leetcode.com/problems/missing-ranges/Given a sorted integer array where the range of elements are [lower, upper] inclusive, return its missing ranges.For example, given [0, 1, 3

原题网址：https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific tar

原题网址：https://leetcode.com/problems/intersection-of-two-arrays-ii/Given two arrays, write a function to compute their intersection.Example:Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], retu

原题网址：https://leetcode.com/problems/3sum-smaller/Given an array of n integers nums and a target, find the number of index triplets i, j, k with 0  that satisfy the condition nums[i] + nums[j]

原题网址：https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/Given an array where elements are sorted in ascending order, convert it to a height balanced BST.方法：递归，自顶向下。/** *

原题网址：https://leetcode.com/problems/kth-largest-element-in-an-array/Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth dis

原题网址：https://leetcode.com/problems/summary-ranges/Given a sorted integer array without duplicates, return the summary of its ranges.For example, given [0,1,2,4,5,7], return ["0->2","4->5","7

原题网址：https://leetcode.com/problems/merge-intervals/Given a collection of intervals, merge all overlapping intervals.For example,Given [1,3],[2,6],[8,10],[15,18],return [1,6],[8,10],[15,1

原题网址：https://leetcode.com/problems/median-of-two-sorted-arrays/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 t

原题网址：https://leetcode.com/problems/combination-sum-ii/Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to

原题网址：https://leetcode.com/problems/search-insert-position/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

原题网址：https://leetcode.com/problems/search-for-a-range/Given a sorted array of integers, find the starting and ending position of a given target value.Your algorithm's runtime complexity must

原题网址：https://leetcode.com/problems/merge-k-sorted-lists/Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.方法：使用最小堆维护当前最小值。/** * Definition fo

原题网址：https://leetcode.com/problems/3sum-closest/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 integ

原题网址：https://leetcode.com/problems/majority-element-ii/Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. The algorithm should run in linear time and in O(1