#algorithms

Explain the "Quicksort" algorithm. Describe how it works step-by-step, its time and space complexity (best, average, and worst-case), and its main advantages and disadvantages compared to other sorting algorithms like Mergesort.

I need to store a collection of items where I will frequently be adding new items and searching for existing items. The order of items does not matter. What is the most appropriate data structure to use (e.g., Array, Linked List, Hash Table, Tree)? Explain the trade-offs and why your choice is the best for this scenario.

Analyze the time complexity (Big O notation) of the following Python function, which checks if an array contains duplicate values. Explain your reasoning step-by-step. `def has_duplicates(arr): for i in range(len(arr)): for j in range(i + 1, len(arr)): if arr[i] == arr[j]: return True; return False`

Master common algorithm patterns for coding interviews. Patterns: 1. Two Pointers (sorted arrays, palindromes). 2. Sliding Window (subarray problems, max/min in window). 3. Fast & Slow Pointers (cycle detection in linked lists). 4. Merge Intervals (overlapping ranges). 5. Cyclic Sort (missing numbers in range). 6. In-place Reversal (linked list reversal). 7. BFS/DFS (tree/graph traversal). 8. Binary Search (sorted data, optimization problems). 9. Top K Elements (heaps, quickselect). 10. Dynamic Programming (optimization, counting). For each pattern: recognize problem type, apply template, practice 5-10 problems. Use LeetCode, HackerRank.