how to get element from vector c++ 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: vector by index c++

// vector::operator[]
#include <iostream>
#include <vector>

int main ()
{
  std::vector<int> myvector (10);   // 10 zero-initialized elements

  std::vector<int>::size_type sz = myvector.size();

  // assign some values:
  for (unsigned i=0; i<sz; i++) myvector[i]=i;

  // reverse vector using operator[]:
  for (unsigned i=0; i<sz/2; i++)
  {
    int temp;
    temp = myvector[sz-1-i];
    myvector[sz-1-i]=myvector[i];
    myvector[i]=temp;
  }

  std::cout << "myvector contains:";
  for (unsigned i=0; i<sz; i++)
    std::cout << ' ' << myvector[i];
  std::cout << '\n';

  return 0;
}