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C++ Interview Questions in Pune

36 practice questions with answers for C++ interviews in Pune.

C++ jobs in Pune

Pune combines IT-services campuses in Hinjewadi and Kharadi with product, automotive and BFSI technology centres. It has a large mid-level job market for data and QA roles, and interviews are often practical and project-based.

Below are 36 questions that match the mix of service, product and domain employers hiring junior c++ developers in Pune.

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01

Write a function that allocates a 2D matrix safely without raw new and delete.

Pointers and Memory ManagementMedium
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#include <vector> std::vector<std::vector<int>> makeMatrix(int rows, int cols) { return std::vector<std::vector<int>>(rows, std::vector<int>(cols, 0)); } // Faster single-block version: index with r * cols + c struct Matrix { int rows, cols; std::vector<int> data; Matrix(int r, int c) : rows(r), cols(c), data(r * c) {} int& at(int r, int c) { return data[r * cols + c]; } };
02

What is std::string_view and what are its pitfalls?

Modern C++ (C++11 to C++23)Medium
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string_view is a non-owning pointer and length pair that refers to existing characters, so passing it avoids copies and accepts both std::string and literals. The main pitfall is lifetime: it must not outlive the data it views, so returning a string_view to a local string or a temporary dangles. It is also not guaranteed to be null-terminated, so do not pass data() to C functions expecting C strings.
03

Your application is slow and you are asked to optimise it. Where do you start?

Performance, Debugging and Build ToolsMedium
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I start by measuring, not guessing. I define a target, such as p99 under 50 ms, create a repeatable benchmark, and profile with perf to find where time actually goes. Then I fix the biggest hotspot first, usually algorithmic complexity, unnecessary copies, allocations or I/O, and re-measure after each change. I keep correctness tests running and stop when the target is met.
04

What is the difference between a static library and a dynamic library?

Performance, Debugging and Build ToolsEasy
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A static library, .a or .lib, is copied into the executable at link time, giving a self-contained binary but larger size and a rebuild for every library update. A dynamic library, .so or .dll, is loaded at run time and shared between processes, saving memory and allowing updates without relinking, but it needs the right version present on the machine and has a small call overhead.
05

What are the main components of the Standard Template Library?

Standard Template Library (STL)Easy
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The STL has four parts. Containers store data, such as vector, deque, list, map, set and unordered_map. Iterators give a uniform way to traverse containers. Algorithms such as sort, find, accumulate and lower_bound work on iterator ranges. Function objects and lambdas customise algorithms, for example a comparator for sort. Adapters such as stack, queue and priority_queue wrap other containers.
06

A generic average function must accept only numeric types. How would you enforce that?

Templates and Generic ProgrammingMedium
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In C++20 I would constrain it: template <typename T> requires std::is_arithmetic_v<T> double average(const std::vector<T>& v). Passing a vector of strings then fails with a clear constraint error. On C++17 the same check can go in a static_assert or std::enable_if. I would also decide whether bool and char should be allowed, since they are technically arithmetic types.
07

Find the middle node of a linked list in a single pass.

Pointers and Memory ManagementEasy
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Node* middle(Node* head) { Node* slow = head; Node* fast = head; while (fast && fast->next) { slow = slow->next; fast = fast->next->next; } return slow; } // fast moves two steps and slow one step, so slow stops at the middle.
08

What is the difference between a shallow copy and a deep copy?

Pointers and Memory ManagementMedium
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A shallow copy copies pointer members, so two objects share one heap buffer; destroying one leaves the other dangling and causes a double free. A deep copy allocates new memory and copies the contents. The compiler-generated copy constructor copies member by member, so a class owning a raw pointer needs a custom copy constructor and copy assignment, or better, should hold a std::vector or unique_ptr instead.
09

Write a C++20 concept and use it to constrain a function.

Templates and Generic ProgrammingMedium
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#include <concepts> #include <string> template <typename T> concept Printable = requires(T t) { { t.toString() } -> std::convertible_to<std::string>; }; template <Printable T> std::string describe(const T& obj) { return "Item: " + obj.toString(); } struct User { std::string name; std::string toString() const { return name; } }; // describe(User{"Asha"}) compiles; describe(42) fails with a clear message.
10

What is the difference between delete and delete[]?

Pointers and Memory ManagementEasy
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delete destroys a single object created with new. delete[] destroys an array created with new[] and calls the destructor of every element, using an element count the runtime stores with the allocation. Using delete on an array or delete[] on a single object is undefined behaviour and can leak or corrupt the heap. In modern code std::vector or std::unique_ptr<T[]> removes the need for either.
11

Build times have become very slow because heavy templates are included everywhere. How do you speed them up?

Templates and Generic ProgrammingHard
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I would measure first with -ftime-trace or build analyzers to find the costly headers. Then reduce includes with forward declarations, move template-heavy implementation details behind non-template interfaces, use extern template with explicit instantiation for common types, enable precompiled headers and a compiler cache such as ccache, and evaluate C++20 modules where the toolchain supports them well.
12

Compute the sum of a large vector in parallel using std::async.

Multithreading and ConcurrencyMedium
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#include <future> #include <numeric> #include <vector> long long parallelSum(const std::vector<int>& v, int parts = 4) { std::vector<std::future<long long>> futs; std::size_t chunk = v.size() / parts; for (int i = 0; i < parts; ++i) { auto b = v.begin() + i * chunk; auto e = (i == parts - 1) ? v.end() : b + chunk; futs.push_back(std::async(std::launch::async, [b, e] { return std::accumulate(b, e, 0LL); })); } long long total = 0; for (auto& f : futs) total += f.get(); return total; } // C++17 alternative: std::reduce(std::execution::par, v.begin(), v.end(), 0LL)
13

How would you explain polymorphism to a junior developer who has just joined your team?

Object-Oriented Programming in C++Easy
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Situation: a new joiner was confused by virtual functions in our codebase. Task: help them become productive quickly. Action: I used a real example from our code, a Notifier base class with Email and Sms versions, drew how the vtable decides the call at run time, and gave them a small task to add a WhatsApp notifier. Result: they finished it in a day and later explained the idea to the next intern.
14

A program does millions of lookups in a std::map with string keys and is slow. How would you speed it up?

Standard Template Library (STL)Medium
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If ordering is not needed, switch to std::unordered_map and call reserve with the expected size to avoid rehashing. For string keys, use heterogeneous lookup with string_view to avoid building temporary strings. If keys are fixed after loading, a sorted vector with binary search is very cache friendly. I would profile before and after, because hashing long strings has its own cost.
15

Why should we hire you for this C++ developer role?

Performance, Debugging and Build ToolsMedium
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Situation: I have prepared specifically for systems-level roles. Task: show I can contribute quickly. Action: I have built projects such as a multithreaded log analyser and a small key-value store in modern C++, used CMake, GoogleTest and sanitizers, and practised data structures and debugging with gdb. Result: I can write safe, measurable, well-tested code from the first sprint, and I learn fast from code reviews and feedback.
16

Explain unique_ptr, shared_ptr and weak_ptr.

Pointers and Memory ManagementMedium
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unique_ptr has sole ownership, cannot be copied, can only be moved, and costs almost nothing over a raw pointer. shared_ptr keeps a reference count in a control block and destroys the object when the last owner disappears. weak_ptr observes an object owned by shared_ptr without increasing the count; call lock() to get a shared_ptr if it still exists. weak_ptr breaks cycles and suits caches.
17

A C++ server crashes with a segmentation fault in production. How do you debug it?

Performance, Debugging and Build ToolsMedium
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Make sure core dumps are enabled with ulimit -c unlimited or systemd-coredump, and keep debug symbols for release builds. Load the core with gdb binary core, run bt to see the stack trace, then inspect frames and variables. If the stack looks corrupted, reproduce in staging with AddressSanitizer. I would also check logs around the crash time and recent deployments, then add a regression test with the fix.
18

A low-latency service shows occasional latency spikes of several milliseconds. How would you investigate?

Performance, Debugging and Build ToolsHard
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I would first capture latency percentiles and correlate spikes with events. Common causes are heap allocation in the hot path, page faults, lock contention, logging that blocks on I/O, CPU frequency changes and the OS scheduling other work on the same core. Tools include perf, off-CPU flame graphs and tracing. Typical fixes are preallocating memory, pinning threads to isolated cores, async logging and avoiding syscalls in hot paths.
19

What are templates in C++? Explain function and class templates.

Templates and Generic ProgrammingEasy
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Templates let you write code once for many types; the compiler generates a concrete version for each type used. A function template such as template <typename T> T maxOf(T a, T b) works for int, double or std::string. A class template such as template <typename T> class Stack builds containers for any element type. The whole STL, including vector, map and algorithms, is built on templates.
20

Use lambdas with standard algorithms to sort strings by length and count those longer than a limit.

Modern C++ (C++11 to C++23)Easy
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#include <algorithm> #include <string> #include <vector> std::vector<std::string> names = {"Ravi", "Anjali", "Om", "Priyanka"}; std::size_t limit = 4; std::sort(names.begin(), names.end(), [](const std::string& a, const std::string& b) { return a.size() < b.size(); }); auto longCount = std::count_if(names.begin(), names.end(), [limit](const std::string& s) { return s.size() > limit; }); // names: Om, Ravi, Anjali, Priyanka; longCount == 2
21

What is a custom deleter for a smart pointer and when do you need one?

Pointers and Memory ManagementHard
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A custom deleter tells the smart pointer how to release a resource that was not created with plain new. For example std::unique_ptr<FILE, decltype(&fclose)> f(fopen(path, mode), &fclose); closes the file automatically. Deleters are used for C library handles, sockets, OS handles and objects from custom pools. For unique_ptr the deleter is part of the type, while shared_ptr stores it in the control block.
22

What are std::optional, std::variant and std::any?

Modern C++ (C++11 to C++23)Medium
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std::optional<T> holds either a T or nothing, ideal for functions that may not return a value, without using magic values or pointers. std::variant<A, B> is a type-safe union that holds exactly one of the listed types, inspected with std::visit or std::get_if. std::any holds a value of any copyable type and needs any_cast to read it. Prefer optional and variant because they are checked at compile time.
23

What is cache locality and why does it matter for performance?

Performance, Debugging and Build ToolsMedium
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CPUs load memory in cache lines, usually 64 bytes, and access to L1 cache takes a few cycles while main memory takes hundreds. Code that walks memory sequentially, like iterating a std::vector, uses every byte loaded and lets the prefetcher help. Pointer-heavy structures like linked lists jump around memory and cause cache misses. That is why a vector often beats a list even for insert-heavy workloads.
24

How do you handle a tight deadline when the C++ code you need to change is complex?

Modern C++ (C++11 to C++23)Medium
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Situation: a client needed a protocol change in two days in code I had not touched. Task: deliver safely. Action: I read the tests first, wrote two new tests for the required behaviour, made the smallest change that passed them, and flagged a risky area to my lead early instead of at the end. I logged a refactoring ticket for later. Result: we shipped on time with no regressions and cleaned up the module the next sprint.
25

Tell me about a performance improvement you delivered and how you measured it.

Performance, Debugging and Build ToolsHard
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Situation: our risk calculation batch took 90 minutes and blocked morning reports. Task: bring it under 30 minutes. Action: I profiled with perf and found most time in allocating small objects and a map lookup inside the inner loop. I preallocated buffers, replaced the map with a flat sorted vector and parallelised independent portfolios with a thread pool, validating outputs against the old version. Result: 22 minutes, with identical numbers.
26

What is a deadlock and how do you prevent it?

Multithreading and ConcurrencyMedium
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A deadlock happens when threads wait forever for each other's locks, for example thread A holds m1 and waits for m2 while thread B holds m2 and waits for m1. It needs mutual exclusion, hold and wait, no preemption and circular wait. Prevent it by always locking in a fixed global order, locking several mutexes together with std::scoped_lock, keeping critical sections small and never calling unknown code while holding a lock.
27

How do virtual functions work internally?

Object-Oriented Programming in C++Medium
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Most compilers give each polymorphic class a vtable, a static table of function pointers for its virtual functions. Every object stores a hidden vptr pointing to its class's vtable. A call through a base pointer loads the vptr, looks up the slot and jumps to the right override. The cost is one pointer per object, an indirect call and usually no inlining, which matters only in very hot loops.
28

Solve two sum: return indices of two numbers that add up to a target.

Standard Template Library (STL)Easy
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#include <unordered_map> #include <vector> std::vector<int> twoSum(const std::vector<int>& nums, int target) { std::unordered_map<int, int> seen; // value -> index for (int i = 0; i < static_cast<int>(nums.size()); ++i) { auto it = seen.find(target - nums[i]); if (it != seen.end()) return {it->second, i}; seen[nums[i]] = i; } return {}; } // O(n) time, O(n) space.
29

Write a variadic function that sums any number of arguments and one that prints them.

Templates and Generic ProgrammingMedium
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#include <iostream> template <typename... Args> auto sum(Args... args) { return (args + ...); // unary right fold } template <typename... Args> void printAll(const Args&... args) { ((std::cout << args << ' '), ...); // comma fold std::cout << '\n'; } // sum(1, 2, 3.5) returns 6.5; printAll(1, 'x', 2.5) prints 1 x 2.5
30

What are memory alignment and padding?

Pointers and Memory ManagementHard
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CPUs access data fastest at addresses that are multiples of its size, so the compiler aligns members and inserts padding bytes. A struct of char, int, char is usually 12 bytes, while ordering it as int, char, char gives 8. alignof reports alignment and alignas raises it, for example to 64 bytes to keep data used by different threads on separate cache lines. Packed structs save space but may be slower.
31

Compare std::mutex, lock_guard, unique_lock and scoped_lock.

Multithreading and ConcurrencyMedium
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std::mutex provides lock and unlock, but calling them manually is error-prone. lock_guard is a simple RAII wrapper that locks in the constructor and unlocks in the destructor. unique_lock is more flexible: it can defer locking, unlock early, be moved and is required by condition_variable. scoped_lock, from C++17, locks one or more mutexes at once using a deadlock-avoidance algorithm.
32

Write a program where two threads print odd and even numbers alternately up to 10.

Multithreading and ConcurrencyMedium
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#include <condition_variable> #include <iostream> #include <mutex> #include <thread> std::mutex m; std::condition_variable cv; int n = 1; const int kMax = 10; void printer(int parity) { std::unique_lock<std::mutex> lk(m); while (true) { cv.wait(lk, [&] { return n > kMax || n % 2 == parity; }); if (n > kMax) break; std::cout << n++ << '\n'; cv.notify_all(); } cv.notify_all(); } int main() { std::thread odd(printer, 1), even(printer, 0); odd.join(); even.join(); }
33

What do auto and decltype do?

Modern C++ (C++11 to C++23)Easy
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auto deduces a variable's type from its initialiser, so auto it = m.begin(); avoids long iterator types. It drops top-level const and references unless you write const auto& or auto&. decltype(expr) yields the declared type of an expression without evaluating it, useful in generic code and return types. decltype(auto) keeps reference-ness exactly, which matters when forwarding return values.
34

Overload operator+ and operator<< for a Complex number class.

Object-Oriented Programming in C++Medium
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#include <ostream> class Complex { double re_, im_; public: Complex(double re = 0, double im = 0) : re_(re), im_(im) {} Complex operator+(const Complex& o) const { return Complex(re_ + o.re_, im_ + o.im_); } friend std::ostream& operator<<(std::ostream& os, const Complex& c) { return os << c.re_ << (c.im_ < 0 ? '-' : '+') << (c.im_ < 0 ? -c.im_ : c.im_) << 'i'; } }; // operator<< is a friend non-member so the stream stays on the left side.
35

Why should a base class have a virtual destructor?

Object-Oriented Programming in C++Medium
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If you delete a derived object through a base pointer and the base destructor is not virtual, only the base destructor runs, which is undefined behaviour and typically leaks the derived part's resources. Making the destructor virtual ensures the derived destructor runs first, then the base one. Rule: any class meant to be used polymorphically needs a public virtual destructor, or a protected non-virtual one.
36

A program crashes with terminate called without an active exception when a function returns. What is the cause?

Multithreading and ConcurrencyMedium
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A std::thread object that is still joinable was destroyed, often because the function returned early or threw before reaching join. The std::thread destructor calls std::terminate in that case. Fix it by making sure every thread is joined on all paths, using an RAII guard, or switching to std::jthread, which joins automatically. Be careful with detach, since detached threads may access destroyed data.

Companies with offices in Pune (9)

Product

Microsoft

C++ interview questions

  • 30 questions
  • 5 rounds

Hyderabad, Bengaluru, Noida +2

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Product

Google

C++ interview questions

  • 30 questions
  • 5 rounds

Bengaluru, Hyderabad, Gurugram +2

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Product

Amazon

C++ interview questions

  • 30 questions
  • 5 rounds

Bengaluru, Hyderabad, Chennai +2

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Product

Oracle

C++ interview questions

  • 30 questions
  • 5 rounds

Bengaluru, Hyderabad, Noida +2

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Hardware & semiconductors

Cisco

C++ interview questions

  • 30 questions
  • 5 rounds

Bengaluru, Pune, Chennai

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Hardware & semiconductors

NVIDIA

C++ interview questions

  • 30 questions
  • 5 rounds

Pune, Bengaluru, Hyderabad

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Hardware & semiconductors

Siemens

C++ interview questions

  • 30 questions
  • 5 rounds

Mumbai, Bengaluru, Pune

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IT services

KPIT Technologies

C++ interview questions

  • 30 questions
  • 4 rounds

Pune, Bengaluru

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IT services

Tata Elxsi

C++ interview questions

  • 30 questions
  • 4 rounds

Bengaluru, Thiruvananthapuram, Chennai +1

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Frequently asked questions

Which companies hire C++ professionals in Pune?

Companies with large offices in Pune include Microsoft, Google, Amazon, Oracle, Cisco, NVIDIA, Siemens, KPIT Technologies, Tata Elxsi. Use their company pages below to practise employer-specific sets.

Are C++ interviews in Pune different from other cities?

The questions depend more on the company than the city. Pune's mix of employers decides the style: It has a large mid-level job market for data and QA roles, and interviews are often practical and project-based

How do I find C++ jobs in Pune?

Shortlist companies with Pune offices, keep your CV focused on C++ projects, apply on company career pages and job portals with the Pune filter, and practise the questions on this page before each interview.

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