Hash table
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This document discusses hash tables, which are data structures that use a hash function to map keys to values in an array of buckets. Hash tables provide O(1) time performance for operations like insertion, search and deletion on average by distributing entries uniformly across the buckets. Collisions, where two keys hash to the same value, are resolved using techniques like separate chaining or open addressing. The document covers topics like choosing good hash functions, collision resolution methods, dynamic resizing, and applications of hash tables.
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Hash tables
The document discusses hash tables and how they can be used to implement dictionaries. Hash tables map keys to table slots using a hash function in order to store and retrieve items efficiently. Collisions may occur when multiple keys hash to the same slot. Chaining is described as a method to handle collisions by storing colliding items in linked lists attached to table slots. Analysis shows that with simple uniform hashing, dictionary operations like search, insert and delete take expected O(1) time on average.
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The document discusses hash tables and their use for efficient data retrieval. It begins by comparing the time complexity of different data structures for searching, noting that hash tables provide constant time O(1) search. It then provides examples of using hash tables to store student records and complaints by number. Key aspects covered include hash functions mapping data to table indices, minimizing collisions, open and closed addressing for collisions, and linked lists or probing as solutions. Types of hash functions and their parameters are defined. The document aims to explain the core concepts of hashing, hash functions, hash tables and approaches for handling collisions.
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The document discusses hash tables and hashing techniques. It describes how hash tables use a hash function to map keys to positions in a table. Collisions can occur if multiple keys map to the same position. There are two main approaches to handling collisions - open hashing which stores collided items in linked lists, and closed hashing which uses techniques like linear probing to find alternate positions in the table. The document also discusses various hash functions and their properties, like minimizing collisions.
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This document discusses hashing techniques for implementing symbol tables. It begins by reviewing the motivation for symbol tables in compilers and describing the basic operations of search, insertion and deletion that a hash table aims to support efficiently. It then discusses direct addressing and its limitations when key ranges are large. The concept of a hash function is introduced to map keys to a smaller range to enable direct addressing. Collision resolution techniques of chaining and open addressing are covered. Analysis of expected costs for different operations on chaining hash tables is provided. Various hash functions are described including division and multiplication methods, and the importance of choosing a hash function to distribute keys uniformly is discussed. The document concludes by mentioning universal hashing as a technique to randomize the hash function
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Hashing is a technique used to store and retrieve information quickly by mapping keys to values in a hash table using a hash function. Common hash functions include division, mid-square, and folding methods. Collision resolution techniques like chaining, linear probing, quadratic probing, and double hashing are used to handle collisions in the hash table. Hashing provides constant-time lookup and is widely used in applications like databases, dictionaries, and encryption.
AVL Tree
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Hash tables
The document discusses hash tables and how they can be used to implement dictionaries. Hash tables map keys to table slots using a hash function in order to store and retrieve items efficiently. Collisions may occur when multiple keys hash to the same slot. Chaining is described as a method to handle collisions by storing colliding items in linked lists attached to table slots. Analysis shows that with simple uniform hashing, dictionary operations like search, insert and delete take expected O(1) time on average.
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The document discusses hash tables and hashing techniques. It describes how hash tables use a hash function to map keys to positions in a table. Collisions can occur if multiple keys map to the same position. There are two main approaches to handling collisions - open hashing which stores collided items in linked lists, and closed hashing which uses techniques like linear probing to find alternate positions in the table. The document also discusses various hash functions and their properties, like minimizing collisions.
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An AVL tree is a self-balancing binary search tree that guarantees search, insertion, and deletion operations will take O(log n) time on average. It achieves this by ensuring the heights of the left and right subtrees of every node differ by at most one. When an insertion or deletion causes a height imbalance of two, rotations are performed to rebalance the tree.
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1. The document discusses hashing techniques for implementing dictionaries and search data structures, including separate chaining and closed hashing (linear probing, quadratic probing, and double hashing).
2. Separate chaining uses a linked list at each index to handle collisions, while closed hashing searches for empty slots using a collision resolution function.
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The document discusses hashing techniques and collision resolution methods for hash tables. It covers:
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- Bucket hashing groups hash table slots into buckets to improve performance. Records are hashed to buckets and stored sequentially within buckets or in an overflow bucket if a bucket is full. This reduces disk accesses when the hash table is stored
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Here are the steps to solve this problem:
1) Construct the open hash table with separate chaining for the keys 30, 20, 56, 75, 31, 19 using h(K) = K mod 11:
Index: 0 1 2 3 4 5 6 7 8 9 10
Keys: 30 20 56 75 31 19
2) The largest number of key comparisons for a successful search is 2 (to search the linked list for key 56).
3) The average number of key comparisons is 1 (each key is directly stored without collisions).
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1. Hashing is a technique that is used to map keys to values in a hash table using a hash function. It allows for fast lookup, insertion, and deletion of key-value pairs.
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Hashing is a technique used to map data of arbitrary size to values of fixed size. It allows for fast lookup of data in near constant time. Common applications include dictionaries, databases, and search engines. Hashing works by applying a hash function to a key that returns an index value. Collisions occur when different keys hash to the same index, and must be resolved through techniques like separate chaining or open addressing.
Hashing algorithms and its uses
Hashing algorithms are used to access data in hash tables through a hash function that converts data into a hash value or key. This key is used to determine the position of data in the hash table, allowing for fast lookup. Collisions can occur if different data hashes to the same key, and are resolved through techniques like open addressing, chaining, or rehashing. Hashing provides efficient indexing and retrieval of data in many applications like databases, compilers, and blockchain.
Similar to Hash table (20)
hashing in data strutures advanced in languae java
hashing in data strutures advanced in languae java
Hashing techniques, Hashing function,Collision detection techniques
Hashing techniques, Hashing function,Collision detection techniques
unit-1-dsa-hashing-2022_compressed-1-converted.pptx
unit-1-dsa-hashing-2022_compressed-1-converted.pptx
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3:国家专业人才认证中心颁发入库证书
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一、工作未确定，回国需先给父母、亲戚朋友看下文凭的情况，办理一份就读学校的毕业证【微信41543339】文凭即可
二、回国进私企、外企、自己做生意的情况，这些单位是不查询毕业证真伪的，而且国内没有渠道去查询国外文凭的真假，也不需要提供真实教育部认证。鉴于此，办理一份毕业证【微信41543339】即可
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留信网认证的作用:
1:该专业认证可证明留学生真实身份
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3:国家专业人才认证中心颁发入库证书
4:这个认证书并且可以归档倒地方
5:凡事获得留信网入网的信息将会逐步更新到个人身份内，将在公安局网内查询个人身份证信息后，同步读取人才网入库信息
6:个人职称评审加20分
7:个人信誉贷款加10分
8:在国家人才网主办的国家网络招聘大会中纳入资料，供国家高端企业选择人才
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2、国（境）学习人员提供就业推荐信服务
3、留学人员区块链存储服务
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我们所定的价格是非常合理的，而且我们现在做得单子大多数都是代理和回头客户介绍的所以一般现在有新的单子 我给客户的都是第一手的代理价格，因为我想坦诚对待大家 不想跟大家在价格方面浪费时间
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ViewShift: Hassle-free Dynamic Policy Enforcement for Every Data Lake
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State of Artificial intelligence Report 2023
Artificial intelligence (AI) is a multidisciplinary field of science and engineering whose goal is to create intelligent machines.
We believe that AI will be a force multiplier on technological progress in our increasingly digital, data-driven world. This is because everything around us today, ranging from culture to consumer products, is a product of intelligence.
The State of AI Report is now in its sixth year. Consider this report as a compilation of the most interesting things we’ve seen with a goal of triggering an informed conversation about the state of AI and its implication for the future.
We consider the following key dimensions in our report:
Research: Technology breakthroughs and their capabilities.
Industry: Areas of commercial application for AI and its business impact.
Politics: Regulation of AI, its economic implications and the evolving geopolitics of AI.
Safety: Identifying and mitigating catastrophic risks that highly-capable future AI systems could pose to us.
Predictions: What we believe will happen in the next 12 months and a 2022 performance review to keep us honest.
一比一原版(Chester毕业证书)切斯特大学毕业证如何办理
毕业原版【微信:41543339】【(Chester毕业证书)切斯特大学毕业证】【微信:41543339】成绩单、外壳、offer、留信学历认证（永久存档真实可查）采用学校原版纸张、特殊工艺完全按照原版一比一制作（包括：隐形水印，阴影底纹，钢印LOGO烫金烫银，LOGO烫金烫银复合重叠，文字图案浮雕，激光镭射，紫外荧光，温感，复印防伪）行业标杆！精益求精，诚心合作，真诚制作！多年品质 ,按需精细制作，24小时接单,全套进口原装设备，十五年致力于帮助留学生解决难题，业务范围有加拿大、英国、澳洲、韩国、美国、新加坡，新西兰等学历材料，包您满意。
【我们承诺采用的是学校原版纸张（纸质、底色、纹路），我们拥有全套进口原装设备，特殊工艺都是采用不同机器制作，仿真度基本可以达到100%，所有工艺效果都可提前给客户展示，不满意可以根据客户要求进行调整，直到满意为止！】
【业务选择办理准则】
一、工作未确定，回国需先给父母、亲戚朋友看下文凭的情况，办理一份就读学校的毕业证【微信41543339】文凭即可
二、回国进私企、外企、自己做生意的情况，这些单位是不查询毕业证真伪的，而且国内没有渠道去查询国外文凭的真假，也不需要提供真实教育部认证。鉴于此，办理一份毕业证【微信41543339】即可
三、进国企，银行，事业单位，考公务员等等，这些单位是必需要提供真实教育部认证的，办理教育部认证所需资料众多且烦琐，所有材料您都必须提供原件，我们凭借丰富的经验，快捷的绿色通道帮您快速整合材料，让您少走弯路。
留信网认证的作用:
1:该专业认证可证明留学生真实身份
2:同时对留学生所学专业登记给予评定
3:国家专业人才认证中心颁发入库证书
4:这个认证书并且可以归档倒地方
5:凡事获得留信网入网的信息将会逐步更新到个人身份内，将在公安局网内查询个人身份证信息后，同步读取人才网入库信息
6:个人职称评审加20分
7:个人信誉贷款加10分
8:在国家人才网主办的国家网络招聘大会中纳入资料，供国家高端企业选择人才
留信网服务项目：
1、留学生专业人才库服务（留信分析）
2、国（境）学习人员提供就业推荐信服务
3、留学人员区块链存储服务
→ 【关于价格问题（保证一手价格）】
我们所定的价格是非常合理的，而且我们现在做得单子大多数都是代理和回头客户介绍的所以一般现在有新的单子 我给客户的都是第一手的代理价格，因为我想坦诚对待大家 不想跟大家在价格方面浪费时间
对于老客户或者被老客户介绍过来的朋友，我们都会适当给一些优惠。
选择实体注册公司办理，更放心，更安全！我们的承诺：客户在留信官方认证查询网站查询到认证通过结果后付款，不成功不收费！
办(uts毕业证书)悉尼科技大学毕业证学历证书原版一模一样
原版一模一样【微信：741003700 】【(uts毕业证书)悉尼科技大学毕业证学历证书】【微信：741003700 】学位证，留信认证（真实可查，永久存档）offer、雅思、外壳等材料/诚信可靠,可直接看成品样本，帮您解决无法毕业带来的各种难题！外壳，原版制作，诚信可靠，可直接看成品样本。行业标杆！精益求精，诚心合作，真诚制作！多年品质 ,按需精细制作，24小时接单,全套进口原装设备。十五年致力于帮助留学生解决难题，包您满意。
本公司拥有海外各大学样板无数，能完美还原海外各大学 Bachelor Diploma degree, Master Degree Diploma
1:1完美还原海外各大学毕业材料上的工艺：水印，阴影底纹，钢印LOGO烫金烫银，LOGO烫金烫银复合重叠。文字图案浮雕、激光镭射、紫外荧光、温感、复印防伪等防伪工艺。材料咨询办理、认证咨询办理请加学历顾问Q/微741003700
留信网认证的作用:
1:该专业认证可证明留学生真实身份
2:同时对留学生所学专业登记给予评定
3:国家专业人才认证中心颁发入库证书
4:这个认证书并且可以归档倒地方
5:凡事获得留信网入网的信息将会逐步更新到个人身份内，将在公安局网内查询个人身份证信息后，同步读取人才网入库信息
6:个人职称评审加20分
7:个人信誉贷款加10分
8:在国家人才网主办的国家网络招聘大会中纳入资料，供国家高端企业选择人才
Beyond the Basics of A/B Tests: Highly Innovative Experimentation Tactics You...
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My burning issue is homelessness K.C.M.O.
My burning issue is homelessness in Kansas City, MO
To: Tom Tresser
From: Roger Warren
The Building Blocks of QuestDB, a Time Series Database
Talk Delivered at Valencia Codes Meetup 2024-06.
Traditionally, databases have treated timestamps just as another data type. However, when performing real-time analytics, timestamps should be first class citizens and we need rich time semantics to get the most out of our data. We also need to deal with ever growing datasets while keeping performant, which is as fun as it sounds.
It is no wonder time-series databases are now more popular than ever before. Join me in this session to learn about the internal architecture and building blocks of QuestDB, an open source time-series database designed for speed. We will also review a history of some of the changes we have gone over the past two years to deal with late and unordered data, non-blocking writes, read-replicas, or faster batch ingestion.
在线办理(英国UCA毕业证书)创意艺术大学毕业证在读证明一模一样
学校原件一模一样【微信：741003700 】《(英国UCA毕业证书)创意艺术大学毕业证》【微信：741003700 】学位证，留信认证（真实可查，永久存档）原件一模一样纸张工艺/offer、雅思、外壳等材料/诚信可靠,可直接看成品样本，帮您解决无法毕业带来的各种难题！外壳，原版制作，诚信可靠，可直接看成品样本。行业标杆！精益求精，诚心合作，真诚制作！多年品质 ,按需精细制作，24小时接单,全套进口原装设备。十五年致力于帮助留学生解决难题，包您满意。
本公司拥有海外各大学样板无数，能完美还原。
1:1完美还原海外各大学毕业材料上的工艺：水印，阴影底纹，钢印LOGO烫金烫银，LOGO烫金烫银复合重叠。文字图案浮雕、激光镭射、紫外荧光、温感、复印防伪等防伪工艺。材料咨询办理、认证咨询办理请加学历顾问Q/微741003700
【主营项目】
一.毕业证【q微741003700】成绩单、使馆认证、教育部认证、雅思托福成绩单、学生卡等！
二.真实使馆公证(即留学回国人员证明,不成功不收费)
三.真实教育部学历学位认证（教育部存档！教育部留服网站永久可查）
四.办理各国各大学文凭(一对一专业服务,可全程监控跟踪进度)
如果您处于以下几种情况：
◇在校期间，因各种原因未能顺利毕业……拿不到官方毕业证【q/微741003700】
◇面对父母的压力，希望尽快拿到；
◇不清楚认证流程以及材料该如何准备；
◇回国时间很长，忘记办理；
◇回国马上就要找工作，办给用人单位看；
◇企事业单位必须要求办理的
◇需要报考公务员、购买免税车、落转户口
◇申请留学生创业基金
留信网认证的作用:
1:该专业认证可证明留学生真实身份
2:同时对留学生所学专业登记给予评定
3:国家专业人才认证中心颁发入库证书
4:这个认证书并且可以归档倒地方
5:凡事获得留信网入网的信息将会逐步更新到个人身份内，将在公安局网内查询个人身份证信息后，同步读取人才网入库信息
6:个人职称评审加20分
7:个人信誉贷款加10分
8:在国家人才网主办的国家网络招聘大会中纳入资料，供国家高端企业选择人才
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Hash table
- 1. HASH TABLE VU QUANG TRAN
- 2. EXAMPLE • Design a system to store employees' information using their phone number as key • Operations: Insert, Search, Delete • Some possible data structures: • Array • Linked List • Balanced Binary Search Tree • Direct Access Table
- 3. EXAMPLE • Design a system to store employees' information using their phone number as key • Operations: Insert, Search, Delete • Some possible data structures: • Array: O(n) Search, Delete • Linked List: O(n) Search • Balanced Binary Search Tree: O(log n) All • Direct Access Table: Space Wastage => Hash Table: O(1) All
- 4. BASICS • Data Structure that implements Associative Array • Map key to corresponding value • Use Hash function to compute index of key- value pairs into an array of buckets • O(1) complexity on average and O(n) in worst case
- 5. HASHING • Distribute the entries (key-value pairs) across an array of buckets • Hash function: Map data of arbitrary size to data of fixed size • Two steps: 1. hash = hash_func(key) 2. index = hash % table_size
- 6. CHOOSING A HASH FUNCTION • Easy to compute • Uniform Distribution
- 7. TYPES OF HASH FUNCTION • Two types: • Cryptographic hash • Non-cryptographic hash • Non-cryptographic hash provides weaker guarantees than cryptographic hash in exchange for performance improvements • Example: • Crypto: BLAKE2b, SHA-512, MD5, … • Non-crypto: MurmurHash, xxHash, ... • Cryptographic hash aims to provide certain security guarantees • Main properties of cryptographic hash: • Deterministic • Quick • One-way function • Avalanche effect • Collision resistant • Pre-image attack resistant
- 8. COLLISION RESOLUTION • Two or more keys result in a same hash value • Practically unavoidable • Handling techniques: • Separate chaining • Open addressing
- 9. COLLISION RESOLUTION SEPARATE CHAINING • Make each cell of hash table point to a linked list of records that have same hash function value
- 10. COLLISION RESOLUTION SEPARATE CHAINING • Make each cell of hash table point to a linked list of records that have same hash function value • Advantages: • Simple to implement • Hash table never fills up • Disadvantages: • Cache performance • Space wastage • Search time can become O(n) if chain gets long
- 11. COLLISION RESOLUTION OPEN ADDRESSING • All elements are stored in the hash table itself • Operations: • Insert: Keep probing until an empty slot is found • Search: Keep probing until key is found or an empty slot is reached • Delete: If we simply delete a key, then search may fail. So slots of deleted keys are marked specially as DELETED
- 12. COLLISION RESOLUTION OPEN ADDRESSING Types: • Linear probing: Linearly probe for next slot index = [hash(x) + i] % S
- 13. COLLISION RESOLUTION OPEN ADDRESSING Types: • Linear probing: Linearly probe for next slot => Clustering index = [hash(x) + i] % S
- 14. COLLISION RESOLUTION OPEN ADDRESSING Types: • Linear probing: Linearly probe for next slot => Clustering index = [hash(x) + i] % S • Quadratic probing: Look for i^2 slot in ith iteration index = [hash(x) + i^2] % S
- 15. COLLISION RESOLUTION OPEN ADDRESSING Types: • Linear probing: Linearly probe for next slot => Clustering index = [hash(x) + i] % S • Quadratic probing: Look for i^2 slot in ith iteration index = [hash(x) + i^2] % S • Double hashing: Use another hash function hash2(x) and look for i*hash2(x) in ith iteration index = [hash(x) + i*hash2(x)] % S
- 16. COLLISION RESOLUTION OPEN ADDRESSING Comparison: • Linear probing: • Easy to compute • Best cache performance • Suffers from Clustering • Quadratic probing: • Lies between cache performance and clustering • Double hashing: • Poor cache performance • No clustering • More computation time
- 17. COLLISION RESOLUTION OPEN ADDRESSING • Advantages: • Better cache performance • Better space usage • Disadvantages: • Harder to implement • Hash table may become full • Clustering
- 18. DYNAMIC RESIZING • Load factor = number of entries / number of buckets • When load factor is too low or too high => Dynamic resizing • Approaches: • Complete resizing • Incremental resizing
- 19. USAGE • Associative Array • Database Indexing • Cache • Set • …
- 21. THANK YOU
Editor's Notes
- Associative Array is an abstract data type composed of a collection of (key, value) pairs, such that each possible key appears at most once in the collection.
- Collision occurs when a newly inserted key maps to an already occupied slot in hash table
- Example: Hash function = key % 7
- Space wastage: some buckets may never be used, extra space to store links
- At any point, size of table must be greater than or equal to total number of keys Insert can insert an item in a deleted slot, but search doesn’t stop at a deleted slot.
- Example: Hash function = key % 7
- Clustering: Many consecutive elements form groups and it starts taking time to find a free slot or to search an element
- Better space usage: bucket co the luu key cua bucket khac neu co collision, no extra space for links
- During the resize, allocate the new hash table, but keep the old table unchanged. In each lookup or delete operation, check both tables. Perform insertion operations only in the new table. At each insertion also move r elements from the old table to the new table. When all elements are removed from the old table, deallocate it.