Question

Is it possible to inset values in a std::vector in an non-consecutive manner like,

std::vector<int> Myvector;
//Myvector[0] = 123;
//Myvecotr[2] = 456;
//Myvector[5] = 789;

Answer 1

When your code uses an index for an element that does not yet exist. Or in other words, if your index exceeds (>=) vector::size() then you are accessing a non existent element. Alas you end up in undefined-behaviour.

std::vector<int> Myvector;
Myvector[0] = 123; // boom  Myvector[0] was never created

So you need to add those elements

// the boring way
Myvector.push_back(0);
Myvector.push_back(0);
Myvector.push_back(0);
Myvector.push_back(0);
Myvector[0] = 123; // set element 0 to 123
Myvector[2] = 456; // set element 2 to 456

Or as stated in other answers you set the size (which I’d prefer):

Myvector.resize(5); 

Or state the size from begin on:

std::vector<int> Myvector(5); // 5 elements, all with the value of the default c'tor