Which of these data structures can provide a more secure and performant alternative to a hashmap when handling user authentication data, especially in scenarios prone to hash flooding attacks?
Array
Queue
Linked list
Tree
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(n)
O(log n)
O(1)
Which of the following is NOT a valid mitigation strategy against hash flooding attacks?
Implementing a random salt value in the hash function to make collisions unpredictable.
Using a fixed-size hashmap to limit the maximum number of collisions.
Switching to a different data structure like a tree-based map that offers consistent performance.
Employing a bloom filter to quickly identify and discard potentially malicious input.
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
Separate Chaining
Linear Probing
What mechanism does Java's ConcurrentHashMap employ to allow for concurrent reads and updates while maintaining thread safety?
Fine-grained locking at the bucket level
Read-write locks separating readers and writers
Lock-free data structures using atomic operations
A single global lock for all operations
What is a common disadvantage of using a hashmap with a poorly chosen hash function?
Frequent hash collisions
Inability to handle duplicate keys
Increased memory usage
Slow key generation
In the context of hashmaps, what is a 'universal hash function' primarily designed to protect against?
Denial-of-service attacks caused by hash flooding.
Collisions caused by malicious input specifically crafted to exploit a known hash function.
Data corruption caused by accidental hash collisions between legitimate inputs.
Attempts to guess the keys used in the hashmap by analyzing the distribution of hashed values.
In Python, what is the purpose of the __hash__ method when used in conjunction with dictionaries?
__hash__
To provide a mechanism for iterating over the key-value pairs in the dictionary.
To specify how a custom object should be converted into a hash value for use as a key.
To define a custom sorting order for keys in the dictionary.
To determine the maximum number of elements that can be stored in the dictionary before resizing.
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.
Hash tables cannot store mutable objects as keys; only immutable objects are allowed.
Using mutable keys increases the memory overhead of the hash table.
Mutable keys make the implementation of the hash table significantly more complex.
In the context of hash tables, what does a high load factor indicate?
Faster insertion operations.
A higher probability of collisions.
Lower memory usage.
A more efficient hash function is being used.