Initializing 2D C++ Vectors

main.cpp

#include <iostream>
#include <vector>

using namespace std;

int main()
{
    //=========Initializing 2D vectors==================
    
    int n, m;
    
    //suppose some size taken, from input or otherwise
    n = 4;
    m = 5;
    
    vector<vector<bool> > arr;
    
	//===========================================================================
	//===========================================================================
	//MAIN PART==================================================================
    arr.resize(n);
    for(int i = 0; i < n; ++i)
	{
		arr[i].resize(m);
	}
    //============================================================================
	//============================================================================
	//============================================================================
	
	
	
    //now we can easily access any element and store stuff inside without causing exceptions
    arr[2][2] = true;
    
    
    
    return 0;
}