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Summary - Queue

Enqueue and dequeue items and print the queue in a mini task.

Summary - Queue

In this group you learned what a queue is, enqueue, dequeue, front and back. Queue follows the FIFO principle.

Queue is used in BFS, schedulers and queue systems. Enqueue is O(1), dequeue depends on implementation.

Practice Queue size

Write queue_size(queue). Return the number of elements. Print 4 with print(queue_size([1, 2, 3, 4])).

Starter code

solution.py
def queue_size(queue):
    # Size

Sample solution

solution.py
def queue_size(queue):
    # Size
    return len(queue)
print(queue_size([1, 2, 3, 4]))

Expected output

4

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Summary - Queue: match the terms

Term Meaning
enqueue Add to back
dequeue Remove from front
FIFO First in first out
BFS Graph

2 Queue principle

Question 
Queue follows the ____ principle.
Answer 
Queue follows the FIFO principle.

Explanation: FIFO is right.

3 Which algorithm uses a queue?

  • DFS
  • BFS Correct answer
  • Selection sort
  • Binary search

Explanation: BFS uses a queue.

All lessons in Beginner

1 What is an algorithm?

  1. Algorithm definition
  2. Algorithm properties
  3. Pseudocode
  4. Summary - Algorithm concept

2 Big-O notation

  1. Time complexity
  2. Big-O definition
  3. Comparing complexities
  4. Summary - Big-O

3 Array

  1. What is an array?
  2. Array access
  3. Looping over an array
  4. Summary - Arrays

4 Linear search

  1. Linear search idea
  2. Implementing search
  3. Best and worst case
  4. Summary - Linear search

5 Search project

  1. Project: Overview
  2. Grades array setup
  3. Search function
  4. Print the result

6 Bubble sort

  1. Bubble sort idea
  2. One pass
  3. Full sort
  4. Summary - Bubble sort

7 Selection sort

  1. Selection sort idea
  2. Finding the minimum
  3. Swapping
  4. Summary - Selection sort

8 Insertion sort

  1. Insertion sort idea
  2. Shifting
  3. Placement
  4. Summary - Insertion sort

9 Sorting project

  1. Project: Overview
  2. Price array
  3. Apply sorting
  4. Print the result

10 Recursion basics

  1. What is recursion?
  2. Base case
  3. Recursive step
  4. Summary - Recursion

11 Fibonacci

  1. Fibonacci sequence
  2. Recursive Fibonacci
  3. Call tree
  4. Summary - Fibonacci

12 Factorial

  1. Factorial definition
  2. Recursive factorial
  3. Choosing the base case
  4. Summary - Factorial

13 Recursion project

  1. Project: Overview
  2. Recursive power
  3. Combination
  4. Print the results

14 Binary search

  1. Binary search idea
  2. Left right pointers
  3. Base case
  4. Summary - Binary search

15 Linked list

  1. What is a linked list?
  2. Node definition
  3. Traversing the list
  4. Summary - Linked list

16 Stack

  1. What is a stack?
  2. Push and pop
  3. Peek and is_empty
  4. Summary - Stack

17 Queue

  1. What is a queue?
  2. Enqueue and dequeue
  3. Front and back
  4. Summary - Queue

18 Hash table

  1. What is a hash table?
  2. Hash function
  3. Collision
  4. Summary - Hash table

19 Set

  1. What is a set?
  2. Add and lookup
  3. Intersection and union
  4. Summary - Set

20 Beginner final

  1. Challenge 1
  2. Challenge 2
  3. Challenge 3
  4. Challenge 4