Q121. How does binary search work and what are its pitfalls?
Binary search finds a target in a sorted array by halving the search range each step, giving O(log n). ```python def binary_search(nums, target): lo, hi = 0, len(nums) - ...
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Q122. Compare ArrayList, LinkedList and HashMap.
- ArrayList: array-backed, O(1) random access, amortised O(1) append, O(n) insertion/removal in the middle. Best default for ordered lists. - LinkedList: doubly linked, O...
Q123. What does SQL stand for?
**SQL** stands for **Structured Query Language**. Originally developed at IBM by Donald D. Chamberlin and Raymond F. Boyce in the early 1970s, it was initially named **SE...
Q124. What are streams and what are the four types?
Streams process data in chunks instead of buffering everything, which keeps memory flat for large files and real-time traffic. Four types: - Readable: source of data (fs....
Q125. What is a generator and when should you use one?
A generator is a function that yields values lazily using yield. Calling it returns a generator object that produces items on demand and remembers its position, so memory...
Q126. How do you prevent SQL injection in PHP?
Never concatenate user input into SQL. Use prepared statements with bound parameters, which separate code from data. ```php $stmt = $pdo->prepare('SELECT * FROM users WHE...
Q127. Explain Flexbox vs Grid and when to use each.
- Flexbox is one-dimensional: it distributes space along a single main axis (row or column). Best for toolbars, navigation, card content, alignment, and components whose ...
Q128. Explain generics and give a realistic use case.
Generics let you write code that works over many types while preserving the relationship between input and output types. ```ts function first(items: T[]): T | undefined {...
Q129. What is a prototype chain?
The prototype chain is a core concept in JavaScript’s inheritance model. It allows objects to inherit properties and methods from other objects. When you try to access a ...
Q130. What are the major features of React?
React offers a powerful set of features that have made it one of the most popular JavaScript libraries for building user interfaces: **Core Features:** - **Component-Base...