Coding questions
ONGC Online Assessment
Overview
Here is how public prep guides and student write-ups describe the ONGC online assessment. This is not an official company brochure.
Moved from GATE-centric hiring to CBT+interview for recent E1 engineer/geologist cycles per 2026 explainers.
Usual selection rounds
Rounds students usually mention: Computer Based Test (CBT) → Personal Interview → Medical fitness
| Item | From student reports |
|---|---|
| Platform | CBT |
| Online test summary | Official E1 GT style: 85 MCQs in 2 hours - Domain 40, Aptitude 25, GA 10, English 10. CBT weight 85 + Interview 15. No negative marking reported in syllabus guides. |
| Eligibility notes | As per official advertisement for the post |
| Branches (reported) | Domain-wise (Petroleum/Mechanical/Chemical/Instrumentation/Geology etc.) |
Online test sections
| Section | Questions | Time | Notes |
|---|---|---|---|
| Concerned domain subject | 40 | within 2h total | - |
| Aptitude | 25 | - | - |
| General awareness | 10 | - | - |
| English | 10 | - | - |
Extra notes from sources
- CBT shortlist often ~1:5 for interview with category rules.
- Qualify CBT and interview separately (Gen/EWS/OBC CBT 45%, interview 9/15; SC/ST/PwBD lower thresholds in cited ad).
Sample practice question styles
These are practice questions for speed - not claimed to be from a real ONGC live paper.
Coding Q1: Move zeros
Problem: Move all zeros in an array to the end while keeping the relative order of non-zero elements.
Approach: Two pointers: write non-zeros toward the front, then fill the remainder with zeros. Or swap zeros as you scan.
Complexity: O(n) time, O(1) space
ONGC tip: Restate the problem, sketch a brute-force idea, then tighten it. Call out edge cases (empty input, single element, overflow) before you write code.
Coding Q2: Rotate array
Problem: Rotate an array to the right by k steps. Example: [1,2,3,4,5,6,7], k = 3 → [5,6,7,1,2,3,4].
Approach: Normalize k %= n. Reverse the whole array, reverse the first k elements, then reverse the rest. That yields the rotation in place.
Complexity: O(n) time, O(1) space
ONGC tip: Restate the problem, sketch a brute-force idea, then tighten it. Call out edge cases (empty input, single element, overflow) before you write code.
Coding Q3: First unique character
Problem: Find the first non-repeating character in a string and return its index, or -1 if none exists.
Approach: Count frequencies in one pass (hash map or array of 26 for lowercase). Second pass returns the first index with count 1.
Complexity: O(n) time
ONGC tip: Restate the problem, sketch a brute-force idea, then tighten it. Call out edge cases (empty input, single element, overflow) before you write code.
Coding Q4: Stack with min
Problem: Design a stack that supports push, pop, top, and getMin in average O(1) time.
Approach: Keep a parallel min-stack (or store pairs). When pushing, also push the new minimum. When popping, pop both stacks.
Complexity: O(1) per operation amortized
ONGC tip: Restate the problem, sketch a brute-force idea, then tighten it. Call out edge cases (empty input, single element, overflow) before you write code.
Prep tips from those student reports
- Download current ONGC PDF
- Domain 40Q is the largest chunk
- No negative marking claimed - still accuracy for cutoff
Sources
- ONGC GT CBT Advt 2/2026 (R&P) - notification PDF mirror (other)
- ONGC Engineer Syllabus/Exam Pattern - Testbook (other)
These notes come from public reports and can differ by campus, year, and role. If your college placement email or the official careers/notification PDF says something different, follow that.