Freecharge coding interview
questions, leaked.
3 problems reported across recent Freecharge interviews. Top patterns: hash table, string, sliding window. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
Freecharge's OA is tight: three medium problems, no easy warmup. You're facing Gas Station, LRU Cache, and Longest Substring Without Repeating Characters. Hash tables show up twice, so they're testing whether you can actually code them under pressure, not just name them. The good news: the problem set is narrow and predictable. The bad news: each one has a hidden gotcha. If you blank on greedy logic or the doubly-linked-list mechanics of an LRU eviction mid-OA, StealthCoder runs invisible during screen share and surfaces a working solution in seconds.
Top problems at Freecharge
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Gas Station | MEDIUM | 100.0 | 46% | Array · Greedy |
| 02 | LRU Cache | MEDIUM | 100.0 | 45% | Hash Table · Linked List · Design |
| 03 | Longest Substring Without Repeating Characters | MEDIUM | 89.1 | 37% | Hash Table · String · Sliding Window |
Frequencies derived from public community-tagged interview reports. Click a row to view on LeetCode.
You have a week, maybe less. You can't out-grind the list above. StealthCoder runs invisibly during the actual Freecharge OA. The proctor cannot see it. Screen share cannot detect it. Made by a working FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know.
Get StealthCoder- hash table2 · 67%
- string1 · 33%
- sliding window1 · 33%
- array1 · 33%
- greedy1 · 33%
- linked list1 · 33%
- design1 · 33%
- doubly linked list1 · 33%
All three problems live in medium difficulty, which means Freecharge expects you to handle both algorithmic logic and clean implementation. Hash-table problems dominate the distribution, appearing in LRU Cache and Longest Substring. That tells you they care about your ability to design data structures and avoid O(n^2) brute force. Gas Station is a greedy problem that trips up candidates who don't spot the invariant: if you can't complete the loop from index i, you can skip all indices up to i. LRU Cache is the structural gatekeep, combining hash tables with a doubly-linked list for O(1) eviction. Longest Substring is sliding-window with a hash table for character tracking. Start with the greedy logic of Gas Station to warm up, then own the LRU design, then treat Longest Substring as your confidence closer. StealthCoder is your safety net if the eviction order or pointer manipulation breaks down live.
Companies with similar patterns
If you prepped for Freecharge, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass Freecharge.
Memorizing every problem above in a week is a fantasy. StealthCoder is the hedge: an AI overlay that's invisible during screen share. It reads the problem on screen and surfaces a working solution in under 2 seconds. Made by a working FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Freecharge interview FAQ
Should I code the LRU Cache from scratch or use built-ins?+
Build it from scratch. LRU Cache tests whether you understand doubly-linked-list node manipulation and hash-table indexing together. Built-ins hide the logic Freecharge is measuring. The assessment environment likely won't let you cheat anyway.
What's the minimum I need to drill for Freecharge?+
Gas Station's greedy skip logic, LRU Cache's O(1) get and put with eviction, and Longest Substring's sliding-window hash-table pattern. That's three problems. You can solve all three in two hours if you've seen them before.
Is hash-table theory enough or do I need to code LRU from memory?+
Code it from memory. Freecharge has LRU Cache in their actual OA set, and it's the hardest of the three. If you freeze on pointer updates or miss the doubly-linked-list, you're done. Drill it until your hands know it.
How much time should I budget per problem?+
Gas Station and Longest Substring are 15-20 minutes each if you've drilled them. LRU Cache is 25-30 because of the implementation detail. If you get stuck on LRU after 20 minutes, move on and come back if time allows.
Is greedy the hardest topic on Freecharge's OA?+
No. Gas Station is medium and solvable once you spot the skip logic. The real wall is LRU Cache, which combines three skills at once: hash-table design, doubly-linked-list operations, and state management. That's where most candidates fail.