CPP

how to make a 2d vector in c++

// Create a vector containing n 
//vectors of size m, all u=initialized with 0
vector<vector<int> > vec( n , vector<int> (m, 0));  

2d vector c++ declaration

vector< vector<int>> a(rows, vector<int> (cols));

2d vector cpp

For user defined size:

vector<vector<int>> vec( n ); 
where n -> number of rows

vector<vector<int>> vec( n , vector<int> (m, 0)); 
where n -> number of rows
where m -> number of columns (all initialized with 0)
  

create a 2d vector in c++

// CPP program
#include <iostream>
#include <vector>
using namespace std;
int main()
{
    int n = 3;
    int m = 4;
 
    /*
    We create a 2D vector containing "n"
    elements each having the value "vector<int> (m, 0)".
    "vector<int> (m, 0)" means a vector having "m"
    elements each of value "0".
    Here these elements are vectors.
    */
    vector<vector<int>> vec( n , vector<int> (m, 0));
 
    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < m; j++)
        {
            cout << vec[i][j] << " ";
        }
        cout<< endl;
    }
     
    return 0;
}

2d array c++

int a[2][3]= {
        {1, 2, 3},
        {4, 5, 6}
    };
    
    cout << a[1][1]; // Output is 5

2D vector in cpp

// CPP program
#include <iostream>
#include <vector>
using namespace std;
int main()
{
    int n = 3;
    int m = 4;
  
    /*
    We create a 2D vector containing "n"
    elements each having the value "vector<int> (m, 0)".
    "vector<int> (m, 0)" means a vector having "m"
    elements each of value "0".
    Here these elements are vectors.
    */
    vector<vector<int>> vec( n , vector<int> (m, 0)); 
  
    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < m; j++)
        {
            cout << vec[i][j] << " ";
        }
        cout<< endl;
    }
      
    return 0;
}

2D vector in cpp

// CPP program
#include <iostream>
#include <vector>
using namespace std;
int main()
{
    int n = 3;
    int m = 4;
  
    /*
    We create a 2D vector containing "n"
    elements each having the value "vector<int> (m, 0)".
    "vector<int> (m, 0)" means a vector having "m"
    elements each of value "0".
    Here these elements are vectors.
    */
    vector<vector<int>> vec( n , vector<int> (m, 0)); 
  
    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < m; j++)
        {
            cout << vec[i][j] << " ";
        }
        cout<< endl;
    }
      
    return 0;
}

how to create 2d array using vector in c++

vector<vector<int>> vec(N, vector<int> (M, INT_MAX));

Explanation::
vector<vector<int>> -- will take the formed container
N -- Think like row of 2d Matrix
vector<int> (M, INT_MAX) -- In each row, there is again a vector associated with it, 
that will formed 2d array.

2d array c++

//* 2D arrays
int n, m;
cout << "Enter row and column: ";
cin >> n >> m;
int arr[n][m];
for (int i = 0; i < n; i++)
{
  for (int j = 0; j < m; j++)
  {
    cin >> arr[i][j];
  }
}

cout << "
Showing array
";

for (int i = 0; i < n; i++)
{
  for (int j = 0; j < m; j++)
  {
    cout << arr[i][j] << " ";
  }
  cout << endl;
}