C/C++ Syllabus to follow

Order arrangement in terms of frequency/no. of times question asked by interviewer
---------------------------

Smart pointers and types such as unique_ptr, weak_ptr, auto_ptr and shared_ptr and difference between them (https://aticleworld.com/unique-pointer-in-cpp/) ,  moving ownership , typecasting of smart pointers and <memory>
Thread api(std::thread) in C++  --> #include <thread>,  --> write a std::thread program
Concurrency and thread synchronization mechanism like Locks , semaphores such as lock_gaurd, mutex, unique_lock, scoped_lock, producer-consumer, condition variables etc,
algorithm.h functions such as reverse(), rotate() , count() etc.
OOPs questions like type of constructors/destructors like pure virtual constructor, copy constructor, explicit constructor, virtual constructor, private constructor, typecasting constructor, constness of this, move constructor(move semantics), private destructor etc.

Design pattern such as singleton will always ask
Virtual, run-time polymorphism example code and applications, vptr and vtable
Function overloading with different combinations of arguments such as default argument, const keyword, static keyword, array & pointers and advanced topics of overloading function using template specialization and type_traits(write a single function to take any level of pointers)

map, vector, string , list, bitset and the difference between them, datastructure used to implement them, Time complexity for insertion, updation, deletion, API functions and operator functions
(if you know all library function std::set then unordered_set & multiset will have library function as set, std::list will aso have same functions as std::forward_list ,similar in case of std::map, std::multimap & std::unordered_map)
iostream such as cin, cout overloading

What is SOLID Principles ? Examples of each of solid principles in c++ code ?

2nd Round of interview will have code fragments/code snippets of 30-40 lines only(very difficult), not theoretical or verbal questions(https://www.geeksforgeeks.org/c-programming-multiple-choice-questions/)

Coding guidelines (C++ 11/17)
-----------
In C++11/17 most important is combination of auto, lambda and for-each loop

//map
for(auto &[key,value] : m) // key, value scope is limited to for-each loop
{
    cout << m[key]++;
  value =  5;
   cout << key << " " << value;
}
or
for(const auto &[key,value] : m) // const for not modifying map , only printing or accessing element is legal
{
    cout << m[key];
   cout << key << " " << value;
}

//vector
for(auto &x: v)
{
    x = 5 // x represents v[i], we are assigning v[i]=5
     cout << x;
}

//string access by index
for(auto &x: str)
{
     x = '\0';
     cout << x;
}

Rest in coding guidelines you need to know library functions and headers

100 Common coding problems( Solve using above Coding guidelines)
-----------------

https://www.geeksforgeeks.org/cpp-coding-interview-questions-and-answers/  

If you get stuck use AI fr code generation, undestanding and optimization like chatgpt, krutrim, perplexity.ai

https://www.changjiangcai.com/studynotes/2020-Interview-C++-Questions-C

https://www.hipeople.io/interview-questions/cpp-interview-questions

https://www.testgorilla.com/blog/cpp-interview-questions-sample-answers/

C++ MCQ's Coding/Code snippet questions only, it will be difficult level (Round 2 only asks difficulty level)
-----------------------------------

https://tests4geeks.com/cpp-online-test

https://letsfindcourse.com/technical-questions/cplusplus-mcq-question

https://heavycoding.com/c-programming-multiple-choice-questions/

https://cppquiz.org/quiz/question/323

https://www.geeksforgeeks.org/c-programming-multiple-choice-questions/

https://www.algbly.com/More/MCQs/Cpp-mcq/Cpp-operators.html

https://www.cppbuzz.com/c++/mcqs/c++-multiple-choice-questions

https://www.cranesvarsity.com/cplusplus-programming-mcq-interview-questions/

https://www.geeksforgeeks.org/quiz-corner-gq/

https://mindmajix.com/cpp-interview-questions

C++ Tutorial
---------

https://www.learncpp.com/

https://www.educative.io/answers

Sample test
----

https://www.testgorilla.com/blog/cpp-interview-questions-sample-answers/