Check out example codes for "2d vector". It will help you in understanding the concepts better.

Code Example 1

``````#include <bits/stdc++.h>
using namespace std;
int main()
{
int rows = 2;
int cols = 2;
int val = 1;
vector< vector<int> > v(rows, vector<int> (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;}``````

Code Example 2

``````#include<bits/stdc++.h>
using namespace std;

int main(){
int n = 3;
int m = 4;

// Create a vector containing n
//vectors of size m.
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<< "\n";
}

return 0;
}``````

Code Example 3

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

Code Example 4

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

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