This is DSA Question. I’m getting at error at runtime

There 2d array ( matrix ) randomly filled by 1 and 0.
When you click on a cell, it changes its
state, and all other cells in the same row,
column(along the X, Y) also change.
The goal is to write a function called unlock() that makes
sure all cells in the matrix are unlocked.

i have problem in understanding the v_unshift function as it checks for v->ofs as 0 and creates a sublist ,it means sublist is full , but in the initial instance of vlist creation it has a sublist and ofs as 0 ,then why it needs to create a sublist in first insertion.
also please explain the ofs and buf as i want to understand it more better.

How would you call this data structure? At first I thought it was a memory arena, but then I read some articles and realised that proper arena implementation would be much harder.

Implement a complete C++ program that analyze the execution time of a given C++ code, and then outputs the overall time complexity (T(n)) of the given program/ code segment and the Big O.
I want to confirm the code from a text file and analyze the time when it is read from the text file containing the code to analyze the time.

With std::set, the time complexity of the operations:
insert: O(log N)
erase: O(log N)
begin, which outputs the min value: O(1)
rbegin, which outputs the max value: O(1)
Seems they have the same complexity requirement as a heap data structure.
So, can I use std::set as a heap data structure?

I am facing a problem with my semester-end project for Data Structures and Algorithms. After discussions with my teacher and classmates, we made some changes to our proposal. We now need to add a “search book by campus” functionality. The requirements are:

In GCC, there is an extension library called pb_ds, which provides a few useful data structures. However, it heavily uses libstdc++’s internal files, making it unable to use with other compilers.

I’m looking to implement a data structure in C++ that allows me to access rows and columns in a contiguous manner. In other words, I want to ensure that when I sequentially access rows, say row [0], row [1], row [2], they are stored contiguously in memory, and similarly, when I sequentially access columns, say column [0], column [1], column [2], they are also stored contiguously.

So I was training to solve problems with old tracks of old mock interview videos and I came across this track: