CareerCup

dynamic array

You can use the double pointer which will hlp to access the each element by O(1) complexity. When the vector tries to grow, use placement new to allocate the pointer next to previously allocated one. After this allocate memory for data.

STL Vectors have been implemented as dynamic arrays. A dynamic array is capable of reallocating its underlying buffer as soon as its current capacity has exhausted (i.e. an attempt is made to insert n+1th element while the current capacity is only n).
In case of default constructor : No memory is allocated.
In case of constructor vector avec(10), where the capacity is given by the argument, allocate array of size 10 on heap. (there must be a default constructor for this for the given object type).
When the vector need to expand, it first allocate memory that is double of current capacity.
Now it copies all its current elements in the newly allocated array.
then it destroys the old arrays (delete []).