Coding Round Preparation for Campus Placements: Complete Guide with Topics & Timeline

Service companies (TCS, Infosys, Wipro, Cognizant, Accenture): Easy to medium. 1-2 problems, 30-45 min. Topics: arrays, strings, basic sorting, simple math. LeetCode easy is sufficient.

Product companies (Amazon, Microsoft, Google, Meta): Medium to hard. 2-3 problems, 60-90 min. Topics: trees, graphs, DP, system design. LeetCode medium + some hard.

Fintech (Goldman Sachs, JP Morgan, Morgan Stanley): Medium. 2 problems, 60 min. Focus on DP, arrays, and correctness. Less emphasis on optimization.

Startups (Swiggy, Zomato, PhonePe, Razorpay): Medium. 2 problems, 60 min. Often domain-related (e.g., delivery routing for Swiggy).

Arrays: reverse, rotate, prefix sum, Kadane's algorithm, Dutch national flag, two pointers.

Strings: palindrome, anagram, pattern matching (KMP), character frequency, string compression.

Hash maps: frequency counting, two-sum, group anagrams, first non-repeating character.

Linked lists: reverse, cycle detection (Floyd's), merge sorted lists, find middle, remove Nth from end.

Stacks: valid parentheses, next greater element, largest rectangle, monotonic stack, evaluate expression.

Queues: level order traversal, sliding window maximum, implement stack using queues.

Trees: traversals (inorder, preorder, postorder, level order), BST operations, LCA, diameter, mirror.

Graphs: BFS, DFS, Dijkstra, topological sort, connected components, cycle detection.

DP: 1D (fibonacci, climbing stairs, house robber), 2D (LCS, edit distance, 0/1 knapsack), on arrays, on strings, bitmask.

Greedy: activity selection, fractional knapsack, Huffman coding basics.

Bit manipulation: XOR tricks, count set bits, single number, subset generation.

Math: GCD/LCM, prime sieve, modular arithmetic, factorial.

LeetCode: Best overall. Use company tags to filter problems by target company. Start with Blind 75, then move to company-specific lists.

HackerRank: Good for beginners. The 'Problem Solving' certification is recognized by some companies. Used by TCS and Infosys for their OA platforms.

GeeksforGeeks: Best for Indian company preparation. Company-specific articles like 'TCS coding questions' and 'Infosys SP questions' are curated.

NeetCode: Video explanations for Blind 75 patterns. Use when you're stuck and need to understand the approach.

Codeforces: Only if you're targeting competitive companies like Google, Meta, or quant firms. Overkill for TCS/Infosys.

Apply PYQs: Company-wise previous year coding questions at /pyqs — 64+ companies with real OA problems.

Days 1-30 (Beginner): Master one language (C++ or Java or Python). Learn basic data structures: arrays, strings, hash maps, linked lists, stacks, queues. Solve 40 easy problems on LeetCode.

Days 31-60 (Intermediate): Trees, graphs, DP basics. Solve 40 medium problems. Focus on patterns: two pointers, sliding window, BFS/DFS, 1D DP. Start company-specific PYQ practice from Apply /pyqs.

Days 61-75 (Advanced): 2D DP, graph algorithms (Dijkstra, topological sort), greedy. Solve 20 medium-hard problems. Take timed contests on LeetCode.

Days 76-90 (Interview-ready): Mock coding interviews. Use Apply's mock interview at /mock-interview with coding enabled. Solve 10 problems under 30-minute timed conditions. Review all mistakes from the past 90 days.

Step 1 (2 min): Read the problem carefully. Ask clarifying questions: input constraints, edge cases, output format.

Step 2 (3 min): Think of a brute force approach. Say it aloud. "The naive approach would be O(n²) by checking all pairs..."

Step 3 (3 min): Optimize. Look for patterns: hash map for O(1) lookup, two pointers for sorted arrays, sliding window for subarray problems.

Step 4 (10 min): Write code. Use meaningful variable names. Handle edge cases (empty input, single element, negative numbers).

Step 5 (5 min): Trace through with a test case. Check for off-by-one errors, null pointers, array bounds.

Step 6 (2 min): Discuss time and space complexity. "This solution is O(n) time and O(n) space because of the hash map."

Don't start coding before understanding the problem — 70% of failures are from misunderstanding the question.

Don't stay silent — think aloud. Even if you can't solve it, showing your thought process gets partial credit.

Don't forget edge cases — empty array, single element, negative numbers, very large input. Interviewers test these.

Don't optimize prematurely — get a working solution first, then optimize. A correct O(n²) is better than a broken O(n).

Don't panic if stuck — ask for a hint. Interviewers prefer candidates who communicate over those who sit silently for 20 minutes.

TCS: Practice from TCS PYQs on Apply. Focus on arrays, strings, basic math. Check /prepare/tcs-nqt-preparation.

Infosys: SP role needs harder coding — DP, trees, graphs. Check Infosys PYQs on Apply.

Amazon: Medium/hard LeetCode problems. Focus on trees, graphs, DP. Check Amazon OA questions on Apply /prepare.

Microsoft: C++/Java focus, OOP + DSA. Check Microsoft interview guide on Apply /prepare.

All 64+ companies: Browse Apply's PYQs library at /pyqs for company-specific coding questions.

Apply provides everything: 64+ company PYQs at /pyqs, mock interviews with coding rounds at /mock-interview, and company prep guides at /prepare. All free to start.