Arrays have to be deallocated explicitly if defined dynamically whereas vectors are automatically de-allocated from heap memory. Size of array cannot be determined if dynamically allocated whereas Size of the vector can be determined in O(1) time.

Are vectors dynamic arrays?

A vector is a dynamic array, whose size can be increased, whereas THE array size can not be changed. Reserve space can be given for vector, whereas for arrays you cannot give reserved space. A vector is a class whereas an array is a datatype.

How are vectors allocated?

Internally, vectors use a dynamically allocated array to store their elements. This array may need to be reallocated in order to grow in size when new elements are inserted, which implies allocating a new array and moving all elements to it.