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Questions and Answers
What is the primary feature of Separate Chaining in hash table implementation?
What is the primary feature of Separate Chaining in hash table implementation?
Which method is NOT typically associated with Open Addressing collision resolution?
Which method is NOT typically associated with Open Addressing collision resolution?
In the context of hash functions, what is the purpose of resolving collisions?
In the context of hash functions, what is the purpose of resolving collisions?
What is a potential drawback of Open Addressing in hash table implementations?
What is a potential drawback of Open Addressing in hash table implementations?
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Which of the following statements about hash functions is true?
Which of the following statements about hash functions is true?
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What is the primary purpose of hashing in data structures?
What is the primary purpose of hashing in data structures?
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Which method is used to resolve collisions in a hash table?
Which method is used to resolve collisions in a hash table?
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What is a key benefit of using chaining for collision resolution in hash tables?
What is a key benefit of using chaining for collision resolution in hash tables?
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In open addressing, what happens when a collision occurs?
In open addressing, what happens when a collision occurs?
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What is the role of a hash function in a hash table implementation?
What is the role of a hash function in a hash table implementation?
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Study Notes
Advanced Data Structure - Hashing
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Hashing is a technique used to store and retrieve data.
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Hashing uses a hash function to compute an index into an array called a hash table.
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Common types of Hashing techniques include:
- Open Addressing
- Linear Probing
- Quadratic Probing
- Double Hashing
- Separate Chaining
- Open Addressing
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Hash function:
- A function that takes a key (input) and returns a hash value (index).
- A crucial element of hashing, dictates data placement in the hash table.
- Typically utilizes the modulo operator (
%) to map the key to an index, often with a hash table size (e.g., 8).
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Open Addressing:
- If a collision (multiple keys produce the same hash value) occurs, a probing strategy (finding an empty slot) is employed to avoid collisions.
- Linear Probing
- Simple.
- Probe consecutive slots from the original hash value until an empty slot.
- Can encounter clustering problems (consecutive occupied slots making searching inefficient). -Quadratic Probing
- Employs a quadratic function to calculate the next slot for probing.
- Less prone to clustering than Linear Probing.
- Double Hashing
- A collision resolution method that involves both a primary hash function and a secondary hash function
- More complex.
- Produces relatively even distribution within the hash table when correctly designed, making collision resolution more robust.
- Linear Probing
- If a collision (multiple keys produce the same hash value) occurs, a probing strategy (finding an empty slot) is employed to avoid collisions.
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Separate Chaining:
- Handles collisions by storing the elements that hash to the same index in a linked list.
- A collision does not cause re-probing.
- Each slot in the hash table functions as a head of the linked list when there is more than one element with the same hash value.
- Typically easier to implement and maintain than open addressing.
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Example values:
- Example input: 26, 30, 70, 45, 13
- Example hash table size: 8
- Example probing sequence for 70: 6,5,4...
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Key takeaway: Different probing techniques in open addressing and separation chaining determine handling methods for hash collisions.
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