Data Structures & Algorithms: Interview Preparation Guide
Complete guide to DSA interview preparation covering essential data structures, algorithms, and problem-solving patterns.
Data structures and algorithms remain the foundation of technical interviews at top tech companies. This guide covers the essential concepts and patterns.
Essential Data Structures
Arrays and Strings
Key patterns:
- Two pointers: Start/end, fast/slow
- Sliding window: Fixed or variable size
- Prefix sum: Range queries in O(1)
- Binary search: Sorted arrays, search space
Linked Lists
Common problems:
- Reverse linked list (iterative and recursive)
- Detect cycle (Floyd's algorithm)
- Merge sorted lists
- Find middle element (fast/slow pointers)
Trees and Graphs
Key concepts:
- Tree traversals: Inorder, preorder, postorder, level-order
- BST operations: Insert, delete, search, validate
- Graph traversals: BFS, DFS
- Shortest path: Dijkstra, Bellman-Ford
- Topological sort: Khan's algorithm, DFS-based
Algorithm Patterns
Dynamic Programming
DP solves problems by breaking them into overlapping subproblems. Identify: optimal substructure and overlapping subproblems. Approaches: top-down (memoization) or bottom-up (tabulation).
Common DP patterns:
- 0/1 Knapsack: Subset sum, partition
- Unbounded Knapsack: Coin change, rod cutting
- LCS/LIS: Longest common subsequence, longest increasing
- Matrix chain: Optimal parenthesization
- DP on trees: House robber III, diameter
Backtracking
Backtracking explores all possibilities by building candidates incrementally and abandoning invalid paths. Used for: permutations, combinations, N-queens, Sudoku solver.
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