?What are the primary differences between an array and a linked list

The primary differences between an array and a linked list are: Memory Allocation: Array: Uses contiguous memory allocation. All elements are stored in consecutive memory locations, which makes indexing very efficient. However, resizing an array can be costly as it may require copying all elements to a new location. Linked List: Uses non-contiguous memory allocation. Elements, or nodes, are scattered throughout memory and are connected via pointers. This makes resizing easy as it simply involves adjusting pointers, but indexing is less efficient. Access Time: Array: Offers O(1) time complexity for accessing elements by index, making it very fast for retrieval operations. Linked List: Has O(n) time complexity for accessing elements, as you may need to traverse the list from the head node to the desired node. Insertion and Deletion: Array: Inserting or deleting elements can be costly (O(n)) as it may require shifting elements to maintain order. Linked List: Insertion and deletion are more efficient (O(1)) if the node to insert or delete is known, as it only involves updating pointers. Example: cpp Copy code // Array int arr[5] = {1, 2, 3, 4, 5}; // Linked List struct Node { int data; Node* next; }; Node* head = new Node(); head->data = 1; head->next = new Node(); head->next->data = 2;

?How does a hash table provide efficient data retrieval, and what is a common issue associated with it

A hash table provides efficient data retrieval through the use of a hash function, which maps keys to specific indices in an array where the corresponding values are stored. This allows for average-case O(1) time complexity for both insertions and lookups, making hash tables extremely fast for these operations. Hash Function: The hash function takes an input (the key) and returns an integer (the hash value), which determines the index in the array where the value associated with the key is stored. Direct Access: By computing the index directly from the key, hash tables allow for constant-time access to data, provided that the hash function distributes keys uniformly across the array. Common Issue - Collisions: Definition: A collision occurs when two different keys hash to the same index. Handling Collisions: There are several strategies to handle collisions, including: Chaining: Each index in the array points to a linked list of entries that hash to the same index. Open Addressing: When a collision occurs, the algorithm searches for the next available slot in the array (using techniques like linear probing, quadratic probing, or double hashing). Example: cpp Copy code // Hash function example int hashFunction(int key) { return key % tableSize; // Simple modulo operation } // Chaining example struct Node { int key; int value; Node* next; }; Node* hashTable[tableSize]; Understanding these differences and mechanisms helps in selecting the appropriate data structure for various applications, optimizing performance and resource usage.

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