declaring 2d vector in c++ code example

Example 1: 2d vector c++ declaration

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

Example 2: 2d vector

#include 
using namespace std;
int main() 
{
  int rows = 2;
  int cols = 2;
  int val = 1;
  vector< vector > v(rows, vector (cols, val));  /*creates 2d vector “v[rows][cols]” and initializes all elements to “val == 1” (default value is 0)*/
  v[0][0] = 5;
  v[1][1] = 4;
  cout << v[0][0] << endl; //Output: 5cout << v[1][0] << endl; //Output: 1return 0;}

Example 3: initialising 2d vector

// Initializing 2D vector "vect" with 
// values 
vector > vect{ { 1, 2, 3 }, 
                           { 4, 5, 6 }, 
                           { 7, 8, 9 } };