You are designing a system to store and retrieve frequently accessed data with high performance. Which of the following hash table collision resolution strategies would generally offer the BEST performance under high load factors?
Quadratic Probing
Double Hashing
Linear Probing
Separate Chaining
What is the primary reason for using a prime number as the size of a hash table in many implementations?
To make the implementation of the hash table simpler.
To ensure an even distribution of keys across the hash table, reducing collisions.
To minimize the memory usage of the hash table.
To increase the speed of hash function computation.
In the context of hashmaps, what is a 'universal hash function' primarily designed to protect against?
Collisions caused by malicious input specifically crafted to exploit a known hash function.
Attempts to guess the keys used in the hashmap by analyzing the distribution of hashed values.
Data corruption caused by accidental hash collisions between legitimate inputs.
Denial-of-service attacks caused by hash flooding.
How does using a cryptographic hash function with a random salt improve the security of a hashmap storing user credentials?
It eliminates the possibility of hash collisions.
It prevents unauthorized users from accessing the hashmap's keys.
It makes it significantly harder for attackers to perform rainbow table attacks.
It encrypts the data stored in the hashmap, making it unreadable without the decryption key.
What mechanism does Java's ConcurrentHashMap employ to allow for concurrent reads and updates while maintaining thread safety?
Lock-free data structures using atomic operations
Fine-grained locking at the bucket level
A single global lock for all operations
Read-write locks separating readers and writers
Python dictionaries use open addressing for collision resolution. Which of the following techniques helps mitigate the performance degradation caused by clustering in open addressing?
Using a cryptographic hash function
Robin Hood Hashing
Linear Probing with a prime step size
In the context of hash tables, what does a high load factor indicate?
Lower memory usage.
A higher probability of collisions.
A more efficient hash function is being used.
Faster insertion operations.
Hopscotch hashing aims to improve the performance of open addressing by:
Using multiple hash tables to store keys with different hash values.
Using a dynamic array to resize the table when the load factor gets high.
Limiting the maximum distance a key can be placed from its original hash index.
Employing a binary search tree for efficient collision resolution.
Why is it generally recommended to avoid using mutable objects as keys in hash tables?
Mutable keys can lead to inconsistent state if their values are modified after being inserted into the hash table.
Using mutable keys increases the memory overhead of the hash table.
Mutable keys make the implementation of the hash table significantly more complex.
Hash tables cannot store mutable objects as keys; only immutable objects are allowed.
In a hash table with open addressing using linear probing, suppose we perform a sequence of insertions where each key hashes to the same index. What is the time complexity of the nth insertion in the worst case?
O(n log n)
O(log n)
O(1)
O(n)