Data Structures

Question What is an array? tap to flip ↻ Answer A collection of elements of the same data type stored in contiguous memory locations. Question How is an array element accessed? tap to flip ↻ Answer Using an index (or subscript) that starts from 0 in most programming languages. Question What is the time complexity to access an array element by index? tap to flip ↻ Answer $O(1)$ Question What is a stack? tap to flip ↻ Answer A linear data structure that follows the Last In First Out (LIFO) principle. Question What are the primary operations on a stack? tap to flip ↻ Answer **Push** (insert) and **Pop** (remove), both at the top. Question What is a queue? tap to flip ↻ Answer A linear data structure that follows the First In First Out (FIFO) principle. Question What are the primary operations on a queue? tap to flip ↻ Answer **Enqueue** (insert at rear) and **Dequeue** (remove from front). Question What is a linked list? tap to flip ↻ Answer A linear data structure where each element (node) contains a data part and a pointer to the next node. Question What is a node in a linked list? tap to flip ↻ Answer A structure that holds data and a reference (pointer) to the next node. Question What is dynamic memory allocation? tap to flip ↻ Answer The process of allocating memory at runtime (as opposed to compile time) using functions like `malloc()` or `new`. Question Which function is used to allocate memory dynamically in C? tap to flip ↻ Answer `malloc()` Question What does `malloc()` return on failure? tap to flip ↻ Answer `NULL` pointer. Question What is the difference between `malloc()` and `calloc()`? tap to flip ↻ Answer `malloc()` allocates a single block of uninitialized memory; `calloc()` allocates multiple blocks and initializes them to zero. Question What is the purpose of `free()` in C? tap to flip ↻ Answer It deallocates memory previously allocated by `malloc()`, `calloc()`, or `realloc()`. Question What is a memory leak? tap to flip ↻ Answer A situation where allocated memory is not freed, leading to wasted memory resources. Question How is an array stored in memory? tap to flip ↻ Answer In contiguous memory locations, allowing constant-time access via index. Question What is the time complexity to insert an element at the beginning of an array? tap to flip ↻ Answer $O(n)$ because all existing elements must be shifted. Question What is the time complexity to insert an element at the beginning of a linked list? tap to flip ↻ Answer $O(1)$ if you have a pointer to the head. Question What is a circular queue? tap to flip ↻ Answer A queue where the rear wraps around to the front when the end is reached, efficiently using space. Question What is a stack overflow? tap to flip ↻ Answer An error that occurs when trying to push onto a full stack. Question What is a stack underflow? tap to flip ↻ Answer An error that occurs when trying to pop from an empty stack. Question What is a doubly linked list? tap to flip ↻ Answer A linked list where each node has two pointers: one to the next node and one to the previous node. Question What is the advantage of a linked list over an array? tap to flip ↻ Answer Dynamic size and efficient insertion/deletion at any position (given a pointer). Question What is the disadvantage of a linked list compared to an array? tap to flip ↻ Answer No direct access by index; extra memory for pointers; not cache-friendly. Question What does `realloc()` do? tap to flip ↻ Answer Resizes a previously allocated memory block, preserving existing data.

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Network Topologies

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Call Stack

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stack data structure

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