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Stacks And Queues

Last Updated: Nov 17, 2023
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Contents

Queue Implementation Details

C :

Array / Linked list based implementation as shown in earlier lessons.

C++ :

C style array queue works in C++ as well. However, C++ provides a library implementation of queue as well.

Queue declaration : :
    queue<int> A; // declares an empty queue. 
Push
    A.push(newElement); // Pushes a new element. O(1)
Pop
    A.pop(); // O(1) pop
isEmpty
    A.empty() // O(1) 
Size
    A.size(); // O(1) 
Front
    A.front(); // O(1). Gives the first element. 
JAVA :

Java has a queue similar to C++.

Queue declaration : :
    Queue A = new LinkedList(); 
Push
    A.add(new Integer(newElement)); // Pushes a new element. O(1)
Pop
    A.poll(); // O(1) pop
isEmpty
     A.isEmpty() // O(1)
Size
    A.size(); // O(1)
Front
    A.peek(); // O(1). Gives the top element. 
PYTHON :

We can use deque as a queue in python.

Queue declaration : :
    A = deque() # declares an empty queue. O(1)
Push
    A.append(newElement) # Put the new Element on the end of the array. O(1).
Pop
    A.popleft() # Pops out the front of the queue
isEmpty
    return (len(A) == 0); # Check if size is 0. O(1)
Size
    return len(A); # O(1)  
Front
    A[0] # O(1)

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