HCL coding interview
questions, leaked.
9 problems reported across recent HCL interviews. Top patterns: string, array, hash table. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
HCL's assessment is heavy on string and array manipulation, with 9 total problems skewed toward the easy side. You're looking at foundational data structure work: Valid Parentheses, Two Sum, Merge Sorted Array, Longest Substring Without Repeating Characters. The majority of problems are EASY to MEDIUM, which means execution speed and clean code matter more than algorithmic wizardry. If you freeze on a hash-table or two-pointer problem during the live assessment, StealthCoder runs invisibly and surfaces the solution in seconds, keeping you moving.
Top problems at HCL
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Valid Parentheses | EASY | 100.0 | 42% | String · Stack |
| 02 | Longest Substring Without Repeating Characters | MEDIUM | 94.0 | 37% | Hash Table · String · Sliding Window |
| 03 | Merge Sorted Array | EASY | 86.3 | 53% | Array · Two Pointers · Sorting |
| 04 | Longest Common Prefix | EASY | 75.5 | 45% | String · Trie |
| 05 | Group Anagrams | MEDIUM | 75.5 | 71% | Array · Hash Table · String |
| 06 | Reverse String | EASY | 75.5 | 80% | Two Pointers · String |
| 07 | Two Sum | EASY | 75.5 | 56% | Array · Hash Table |
| 08 | 3Sum | MEDIUM | 75.5 | 37% | Array · Two Pointers · Sorting |
| 09 | Palindrome Number | EASY | 75.5 | 59% | Math |
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 HCL OA. The proctor cannot see it. Screen share cannot detect it. Built by a senior engineer who knows the OA is theater. This is the script.
Get StealthCoder- string5 · 56%
- array4 · 44%
- hash table3 · 33%
- two pointers3 · 33%
- sorting3 · 33%
- sliding window1 · 11%
- stack1 · 11%
- trie1 · 11%
- math1 · 11%
String problems dominate your prep (5 problems), followed by arrays (4). Hash-table, two-pointers, and sorting each appear 3 times, so you need comfort with those patterns fast. The difficulty spread is forgiving: 6 EASY, 3 MEDIUM, 0 HARD. This tells you HCL is filtering for clean fundamentals and speed, not trick problems. Drill Valid Parentheses and Reverse String first to build confidence, then lock in Two Sum and Merge Sorted Array for the array and hash-table muscle. By the time you sit down, Longest Substring Without Repeating Characters and Group Anagrams should feel automatic. The low-frequency topics like sliding-window, stack, and trie matter less but watch for them. StealthCoder is your hedge if a hash-table or string pattern blindsides you mid-assessment.
Companies with similar patterns
If you prepped for HCL, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass HCL.
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. Built by a senior engineer who knows the OA is theater. This is the script. Works on HackerRank, CodeSignal, CoderPad, and Karat.
HCL interview FAQ
Should I memorize string manipulation or focus on hash-table patterns first for HCL?+
String appears in 5 of 9 problems, so string manipulation is your foundation. Start with Valid Parentheses and Reverse String to build speed, then move into Longest Substring Without Repeating Characters, which combines string, hash-table, and sliding-window. Hash-table patterns (Two Sum, Group Anagrams) follow naturally.
Are two-pointers and sorting worth heavy drilling for this assessment?+
Yes. Both appear 3 times each. Two-pointers shows up in Merge Sorted Array, Reverse String, and 3Sum. Sorting is embedded in Group Anagrams and 3Sum. Practice these back-to-back to own the pattern. You can solve most variations in under 5 minutes once it clicks.
Is the EASY-heavy difficulty split a sign I can skip medium problems?+
No. Six EASY problems warm you up, but the 3 MEDIUM ones (Longest Substring, Group Anagrams, 3Sum) are where mistakes happen. MEDIUM problems test your ability to combine patterns. Solve them last in your prep but under timed conditions to catch edge cases.
How much time should I spend on sliding-window and trie if they only appear once?+
Trie and sliding-window are low-frequency (1 problem each). Don't skip them entirely, but don't spend a week on them either. Sliding-window logic is embedded in Longest Substring anyway. After you nail the main patterns, revisit these as polishing work.
What if I blank on a hash-table problem during the real assessment?+
Hash-table appears in Two Sum, Longest Substring, and Group Anagrams. If you freeze mid-assessment, StealthCoder surfaces a working solution invisibly while you're screen-sharing. You'll stay calm and moving. That said, Two Sum is EASY and foundational, so drill it until it's muscle memory.