# Insert Delete GetRandom O(1)

Insert Delete GetRandom O(1)Design a data structure that supports all following operations in average O(1) time. insert(val): Inserts an item val to the set if not already present. remove(val): Remo

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Insert Delete GetRandom O(1)

Insert Delete GetRandom O(1)Design a data structure that supports all following operations in average O(1) time. insert(val): Inserts an item val to the set if not already present. remove(val): Remo

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Kth Smallest Element in a Sorted Matrix

Kth Smallest Element in a Sorted MatrixGiven a n x n matrix where each of the rows and columns are sorted in ascending order, find the kth smallest element in the matrix. Note that it is the kth smal

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Find K Pairs with Smallest Sums

Find K Pairs with Smallest SumsYou are given two integer arrays nums1 and nums2 sorted in ascending order and an integer k. Define a pair (u,v) which consists of one element from the first array and

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Largest Divisible Subset

Largest Divisible SubsetGiven a set of distinct positive integers, find the largest subset such that every pair (Si, Sj) of elements in this subset satisfies: Si % Sj = 0 or Sj % Si = 0. If there are

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Water and Jug Problem

Water and Jug ProblemYou are given two jugs with capacities x and y litres. There is an infinite amount of water supply available. You need to determine whether it is possible to measure exactly z li

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Count Numbers with Unique Digits

Count Numbers with Unique DigitsGiven a non-negative integer n, count all numbers with unique digits, x, where 0 ≤ x < 10^n. For example:1Given n = 2, return 91. (The answer should be the total nu

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Design Twitter

Design TwitterDesign 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 the user’s news feed. Your design should

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Top K Frequent Elements

Top K Frequent ElementsGiven a non-empty array of integers, return the k most frequent elements. For example:1Given [1,1,1,2,2,3] and k = 2, return [1,2]. Note: You may assume k is always valid, 1 ≤

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Integer Break

Integer BreakGiven a positive integer n, break it into the sum of at least two positive integers and maximize the product of those integers. Return the maximum product you can get. For example:1Given

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Counting Bits

Counting BitsGiven a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1’s in their binary representation and return them as an array. For example:

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House Robber III

House Robber IIIThe thief has found himself a new place for his thievery again. There is only one entrance to this area, called the “root.” Besides the root, each house has one and only one parent ho

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Reconstruct Itinerary

Reconstruct ItineraryGiven a list of airline tickets represented by pairs of departure and arrival airports [from, to], reconstruct the itinerary in order. All of the tickets belong to a man who depa

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Increasing Triplet Subsequence

Increasing Triplet SubsequenceGiven an unsorted array return whether an increasing subsequence of length 3 exists or not in the array. Formally the function should: Return true if there exists i, j,

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Verify Preorder Serialization of a Binary Tree

Verify Preorder Serialization of a Binary TreeOne way to serialize a binary tree is to use pre-order traversal. When we encounter a non-null node, we record the node’s value. If it is a null node, we

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Odd Even Linked List

Odd Even Linked ListGiven a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes. You shou

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Coin Change

Coin ChangeYou are given coins of different denominations and a total amount of money amount. Write a function to compute the fewest number of coins that you need to make up that amount. If that amou

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Bulb Switcher

Bulb SwitcherThere are n bulbs that are initially off. You first turn on all the bulbs. Then, you turn off every second bulb. On the third round, you toggle every third bulb (turning on if it’s off o

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Maximum Product of Word Lengths

Maximum Product of Word LengthsGiven a string array words, find the maximum value of length(word[i]) * length(word[j]) where the two words do not share common letters. You may assume that each word w

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Super Ugly Number

Super Ugly NumberWrite a program to find the nth super ugly number. Super ugly numbers are positive numbers whose all prime factors are in the given prime list primes of size k. For example, [1, 2, 4

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Minimum Height Trees

Minimum Height TreesFor a undirected graph with tree characteristics, we can choose any node as the root. The result graph is then a rooted tree. Among all possible rooted trees, those with minimum h

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Best Time to Buy and Sell Stock with Cooldown

Best Time to Buy and Sell Stock with CooldownSay you have an array for which the ith element is the price of a given stock on day i. Design an algorithm to find the maximum profit. You may complete a

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Range Sum Query - Mutable

Range Sum Query - MutableGiven an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. The update(i, val) function modifies nums by updating the element at ind