2d vector c++ push_back code example

Example 1: get values from a vector of vectors c++

#include <iostream>
#include <vector>
using namespace std;  

int main()
{
    vector<vector<int> > buff;

    for(int i = 0; i < 10; i++)
    {
        vector<int> temp; // create an array, don't work directly on buff yet.
        for(int j = 0; j < 10; j++)
            temp.push_back(i); 
 
        buff.push_back(temp); // Store the array in the buffer
    }

    for(int i = 0; i < buff.size(); ++i)
    {
        for(int j = 0; j < buff[i].size(); ++j)
            cout << buff[i][j];
        cout << endl;
    }

    return 0;
}

Example 2: 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));

Example 3: 2d vector

#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;}

Example 4: c++ 2D vectors

int main() 
{ 
    int row = 5; // size of row 
    int colom[] = { 5, 3, 4, 2, 1 }; 
  
    vector<vector<int> > vec(row);  // Create a vector of vector with size equal to row. 
  	for (int i = 0; i < row; i++) { 
  		int col;  
        col = colom[i]; 
  		vec[i] = vector<int>(col); //Assigning the coloumn size of vector
        for (int j = 0; j < col; j++) 
            vec[i][j] = j + 1; 
    } 
  
    for (int i = 0; i < row; i++) { 
        for (int j = 0; j < vec[i].size(); j++) 
            cout << vec[i][j] << " "; 
        cout << endl; 
    } 
}

Example 5: 2d vector push back

std::vector<std::vector<int>> normal;
for(int i=0; i<10; i++)
{
  	//push a vector each time you loop a row
    normal.push_back(std::vector<int>());
    for(int j=0; j<20; j++)
    {
      	//push an item each time you loop a column
        normal[i].push_back(j);    
    }
}