C++ :

C style arrays work in C++ as well.

However, C++ provides vectors which is much more powerful than C arrays. We will be using C++ vectors in most of the problems on this judge.

Vector declaration :

    vector<int> V; // declares an empty integer array of size 0. O(1) 
    vector<int> V(100, 1); // declares an integer array of size 100 with all elements initialized to 1. O(size)

Accessing ith element :

    V[i] // O(1)

Size ( number of elements ) of the vector :

    V.size()  // O(1)

Adding element to the vector :

    V.push_back(new_value); // new_value will be appended to the vector.  O(1)

Removing element from end of the vector :

    V.pop_back(); // equivalent to size--; O(1)

JAVA :

Java has multiple ways of representing arrays. For the purpose of problem solving on this site, we will limit ourselves to ArrayList.

Array declaration :

    ArrayList<Integer> A = new ArrayList<Integer>(); // declares an empty integer array. O(1)
    ArrayList<Integer> A = new ArrayList<Integer>(B); // creates a copy of list B.  O(size of B)

Accessing ith element :

    A.get(i)     // O(1)

Setting ith element :

    A.set(i, newValue)  // O(1)

Size of the list :

    A.size()  // O(1) operation

Adding elements to the list :

    A.add(newValue); // appends to the end of the list. O(1) operation. 
    A.add(index, newValue); // add the value at specified index. O(size - index) operation. 

PYTHON :

Python too has multiple ways of representing arrays. lists are used primarily for the purpose. In few cases, tuples are used when we desire the array to be immutable ( its desired that no one can change the content of the array ).

List declaration :

    A = []; # declares an empty list. O(1)

Accessing the ith element :

    A[i]  # O(1)

Adding element to the list :

    A.append(newValue); # O(1) 

Size of the list :

    len(A)  # O(1)