INOI Preparation Course: ZIO, ZCO and INOI in C++

Registration for the Indian Computing Olympiad 2027 cycle opens in October 2026, with details announced by IARCS in the second half of September. If your child is in school and has any aptitude for mathematics or programming, the next few weeks are when that decision gets made — and most families miss it simply because nobody told them it was happening.

This INOI preparation course is built directly on the official IARCS syllabus, not on a generic competitive-programming curriculum with an olympiad label attached.

What the Indian Computing Olympiad actually is

The ICO is run annually by IARCS to identify school students with outstanding skill in algorithms and programming, and it selects the team of four that represents India at the International Olympiad in Informatics. It runs as a two-round funnel followed by a training camp.

Round one comes in two forms, and you may sit either or both. The Zonal Informatics Olympiad (ZIO) is a written exam held at centres across the country. The Zonal Computing Olympiad (ZCO) is a programming exam, and it accepts C++, Java or Python. Qualifying through either one takes you to round two.

That first point deserves emphasis because it is so widely misunderstood: ZIO requires no programming whatsoever. It is a reasoning paper. A Class 7 student who is strong at mathematics but has never written a line of code can sit ZIO this year and qualify. Families who assume the computing olympiad is closed to non-programmers routinely skip a year they could have used.

Round two is INOI, the Indian National Olympiad in Informatics, and here the rules tighten sharply. INOI is a programming contest, and the only language allowed is C++. Not Java. Not Python. From INOI, approximately 30 students are selected for the IOI Training Camp, and from that camp comes the team of four.

Put those two facts together and you get the single most important planning consequence in this entire process, which we will return to below.

Who can take part

The ICO is open to all school students across the country, from any board. Any student registered in school up to Class 12 during the academic year is eligible, and there is no lower age limit — a capable Class 6 student may sit it.

The exclusion is strict and catches people out. You must still be in school. A student who has completed Class 12 is no longer eligible, even if they have taken a break and are not enrolled in college, and even if they plan to redo Class 12 for improvement. In practice this means Class 11 is the last comfortable year to begin seriously, and starting earlier is worth a great deal.

Why this course is structured around C++ from the start

Here is the trap. A student prepares in Python because it is what school taught. They qualify through ZIO, which needs no code at all, or through ZCO, which accepts Python. They reach INOI — and discover that INOI accepts C++ only. Now they must learn an unfamiliar language under contest pressure, in the weeks when they should be practising algorithms.

We teach C++ from the beginning for exactly this reason. Not because C++ is a better first language in the abstract, but because it is the language the decisive round requires, and learning it early costs nothing while learning it late costs the year.

For students arriving from Python, the teaching focuses on what Python hid: fixed-width integers that overflow silently, memory and references, the cost of copying a container, and the fact that an out-of-range index is undefined behaviour rather than an error. Those four things account for most of the wrong answers a Python-trained student produces in their first C++ contest.

The syllabus, exactly as IARCS defines it

IARCS states the syllabus plainly: the syllabus for ZIO and ZCO is the list of Basic Topics in its Online Study Material, and the syllabus for INOI and IOITC is the IOI syllabus. We teach to that list rather than to a generic competitive-programming syllabus, because the official list is narrower and more learnable than most coaching covers.

The thirteen basic topics are: introduction, efficiency, searching, sorting, basic graph algorithms, dynamic programming, greedy algorithms, computing shortest paths, heaps, permutations, directed acyclic graphs, computing prefix sums, and sliding window algorithms. That is the whole zonal-round syllabus. It is finite, it is teachable in a school year alongside regular studies, and a student who genuinely owns those thirteen is in a strong position at the zonal stage.

The six advanced topics that carry INOI and the training camp are: advanced graph algorithms, dynamic programming on trees, range queries, network flows, games and strategies, and geometry. These are harder and they are where most of our teaching time goes in the second half of the year.

How the classes actually run

Sessions are live and worked, not lectured. The tutor sets a problem, the student attempts it in real time on a shared editor, and the teaching happens in the gap between the first idea and the correct one. Watching someone else solve a problem builds recognition; being stuck in front of someone who can see where you are stuck builds the ability to solve.

Every data structure is implemented before it is used. A student will use the standard library's priority queue for the rest of their life, but writing a heap once teaches what it costs — and cost, not syntax, is what decides whether a solution passes.

From the midpoint of the course, mock contests run under real conditions: full duration, single sitting, no reference material, scored honestly against subtasks. Each one is followed by a written post-mortem covering which problems were solvable but missed, where the minutes went, which bug cost the most, and what subtask was left on the table. The upsolve matters more than the contest — a student who sits one contest a week and upsolves every problem will overtake one who sits four and upsolves none.

We also teach subtask harvesting explicitly, because it is worth marks immediately. Olympiad problems carry partial scoring, and a brute-force solution that clears an early subtask in ten lines is guaranteed marks banked before any clever approach is attempted. Students who solve in statement order routinely score below students with less ability who solve in order of confidence divided by implementation length.

What doing well opens up

Beyond the olympiad itself, several Indian institutions publish special admission procedures for ICO students. Chennai Mathematical Institute offers direct admission to students who win gold or silver medals at INOI or are selected for IOITC in Class 11 or 12. IIT Kanpur and IIT Gandhinagar offer admission through their olympiad categories for IOITC selection, and IIT Kharagpur, IIT Madras and IIT Mandi do so via SCOPE. IIIT Delhi offers bonus points for INOI and IOITC selection, and IIIT Hyderabad admits through its olympiad category for IOITC selection. Internationally, HKUST has a scholarship scheme for selected IOI and APIO medallists, and NTU Singapore gives special consideration to IOI medallists.

Two honest caveats. First, these are conditional on reaching a high bar — medals at INOI or selection to a camp of roughly thirty students nationally. Second, IARCS itself advises checking directly with each institution about eligibility and procedure, and so do we. We will not tell you this course leads to an IIT seat. We will tell you the route exists, is official, and is published.

The more reliable benefit is the ordinary one: a student who has genuinely learned dynamic programming, graph algorithms and careful C++ by Class 11 is better prepared for JEE-level problem solving, university admission essays that need something real in them, and eventually for engineering work — regardless of how the olympiad itself goes.

Starting now, and what the year looks like

Registration opens in October. In the recent cycle, ZIO fell in mid-November and ZCO in early February, with INOI in mid-February and the training camp in June — so beginning in autumn gives roughly two months to the first zonal window and about five to INOI. Dates shift every year and are published on the IARCS site, which is the only source we ask families to trust for them.

For a student starting from no programming, we would ordinarily target ZIO in the first year, since it needs no code, while building C++ and algorithms underneath for a serious ZCO and INOI attempt the following year. For a student who already programs, the full ZCO-to-INOI route in one cycle is realistic.

Either way, the first session is a diagnostic. We would rather tell you honestly where a student stands, and which of those two plans fits, than sell a package that does not match them. Trial sessions are available before you commit, and we teach students in India, the UAE, Singapore, Qatar and the US on schedules that fit around their school day.