Phonepe

The process consisted of an OA, two technical rounds and an HM round. The OA was heavily DSA-focused, with problems on task assignment, trees/graphs, Codeforces-style problems and bitmask DP. The first problem could be optimized using binary search on the answer, while the second involved identifying routers and regions in a tree. The remaining problems were significantly harder, including Codeforces 1665C and 8C. The key takeaway was to prioritize easier questions and maximize partial points rather than spending too much time on one difficult problem. Technical Round 1 focused on advanced DSA. I was asked Making A Large Island, where we discussed DFS, DSU and component identification. The second problem involved finding the minimum diameter after merging two trees. I had to first establish that the given graphs were actually trees, then derive the tree-diameter approach using two DFS traversals and handle edge cases such as odd diameters. The interviewer also focused heavily on communication and proof of the approach rather than just writing code. Technical Round 2 was more difficult and included dynamic programming and Trie-based problems. I was asked the AtCoder M - Candies problem and had to explain the DP state, transitions and complexity, followed by a dry run and discussion of prefix-sum optimization. The second problem was Maximum Strong Pair XOR II, where I derived the condition y <= 2x and developed a Trie-based solution that stored indices to verify valid elements. The interviewer heavily challenged and dry-ran the approach, so thinking aloud and clearly defending the logic was important. The HM round lasted around two hours and was heavily resume- and system-design-oriented. The interviewer went through almost every detail of my resume and asked behavioural questions about teamwork, conflicts, TPO, professors and my internship. I was also asked about a startup idea and its data flow, which was then turned into a system design discussion for an Autopay system, including failure cases and improvements. Overall, the process strongly emphasized DSA, problem-solving, communication, deep knowledge of one's resume, and the ability to reason through system-design problems.