Paytm's DSA rounds lean on strings, sliding-window patterns, and classic design problems like LRU caches — interviewers also probe complexity discussion and, at senior levels, tie coding questions into prior payments-domain experience. The three problems below are real, recently reported (2025) Paytm questions with full solutions.
Given two strings, find the length of the longest substring that is common to both of them. Unlike a common subsequence, the matched characters must be contiguous in both strings.
Input: s1 = "abcdef", s2 = "zcdefg"
Output: 4
"cdef" appears contiguously in both strings.
Given an array of integers and a window size k, for every contiguous window of size k report the first negative number in that window, or 0 if the window has none.
Input: nums = [12, -1, -7, 8, -15, 30], k = 3
Output: [-1, -1, -7, -15]
Design a data structure that implements a Least Recently Used cache with a fixed capacity, supporting get(key) and put(key, value) in O(1) time each. When the cache is full, put should evict the least recently used entry before inserting the new one.
Input: capacity = 2; put(1,1); put(2,2); get(1); put(3,3); get(2)
Output: get(1) -> 1, then key 2 is evicted, get(2) -> -1
More DSA questions Paytm has asked recently
These topics were reported in verified 2025 Paytm loops. Full problem statements, solutions and explanations for these are part of the Placement-Ready PYQ Kit.
2 more verified DSA questions with full solutions in the full Placement-Ready PYQ Kit
Includes the round context they were asked in, from online assessment through onsite rounds.