Set and Map Operations in Java and Python

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Questions and Answers

What must be true about parent node values in a heap structure?

  • Parent node values are randomly ordered compared to child nodes.
  • Parent node values are greater than child nodes.
  • Parent node values are equal to child nodes.
  • Parent node values are less than or equal to child nodes. (correct)

Which method retrieves but does not remove the root of a heap in Java?

  • poll()
  • get()
  • remove()
  • peek() (correct)

What occurs when attempting to dequeue from an empty Java PriorityQueue?

  • Returns null
  • Returns an empty value
  • No operation is performed
  • Throws an exception (correct)

What is the method to dequeue in Python's PriorityQueue?

<p>get() (A)</p> Signup and view all the answers

Which of the following is the correct method to enqueue an element into a PriorityQueue in Java?

<p>offer() (D)</p> Signup and view all the answers

What describes the main feature of a Max Heap?

<p>Parent node has the largest value. (C)</p> Signup and view all the answers

Which class in Java provides the implementation of PriorityQueue?

<p>PriorityQueue (A)</p> Signup and view all the answers

What operation combines all elements of two sets without duplication?

<p>Union (D)</p> Signup and view all the answers

What is the result of the operation {1, 3, 5} ∩ {3, 4, 5}?

<p>{3, 5} (C)</p> Signup and view all the answers

Which function in Python checks if a PriorityQueue is empty?

<p>empty() (A)</p> Signup and view all the answers

Which set implementation in Java stores elements in natural sorted order?

<p>TreeSet (C)</p> Signup and view all the answers

What is the method to check if a set is a subset of another set in Python?

<p>issubset() (A)</p> Signup and view all the answers

What type of key-value pair storage does a HashMap use in Java?

<p>Hash table (C)</p> Signup and view all the answers

Which operation determines elements only in the first set but not in the second?

<p>Difference (A)</p> Signup and view all the answers

What is the result of {1, 2, 3} ∪ {4, 5} in Python?

<p>{1, 2, 3, 4, 5} (D)</p> Signup and view all the answers

Which Java Map implementation maintains insertion order?

<p>LinkedHashMap (C)</p> Signup and view all the answers

Flashcards

Set Union

Combines all elements from two sets, removing duplicates.

Set Intersection

Finds common elements in two sets.

Set Difference

Finds elements in the first set but not in the second set.

TreeSet (Java)

Stores elements in a sorted order (naturally).

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issubset() (Python)

Checks if a set is a subset of another.

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Hash Table (HashMap)

A data structure used by Java HashMap to store key-value pairs.

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del (Python)

Removes a key-value pair from a dictionary.

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HashMap (Java)

Stores key-value pairs using a hash table, allowing fast lookups.

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Java PriorityQueue retrieval (no removal)

The peek() method retrieves, but does not remove, the head of a PriorityQueue. It returns null if empty

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Python PriorityQueue enqueue

Use the put() method to add elements to a Python PriorityQueue.

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Java PriorityQueue enqueue

The offer() method adds an element to a Java PriorityQueue, returning false if the operation fails.

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Max Heap

A heap where the parent node's value is always greater than or equal to its children.

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Java PriorityQueue initialization

Use the new PriorityQueue() constructor to create a Java PriorityQueue. It does not need comparator unless you need a custom sort order.

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Python PriorityQueue checking emptiness

Use the empty() method to check if a Python PriorityQueue is empty. Returns True if empty, False otherwise.

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Python PriorityQueue dequeue

Use the get() method to dequeue (remove and return) an element from a Python PriorityQueue.

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Java PriorityQueue dequeue (remove)

The poll() method retrieves and removes the head of a Java PriorityQueue, returning null if the queue is empty.

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Study Notes

Set Operations and Implementations

  • Union: Combines all elements of two sets without duplicates
  • Intersection: Returns common elements in two sets
  • Difference: Returns elements in the first set but not in the second set
  • Subset: A set containing all elements from another set (issubset() in Python)
  • HashSet (Java): Stores elements without maintaining order; fast lookups
  • TreeSet (Java): Stores elements in natural sorted order
  • LinkedHashSet (Java): Stores elements in insertion order.
  • Methods for Sets:
    • issubset(): Python method to check if a set is a subset of another set

Key-Value Pair Storage

  • HashMap (Java): Uses a hash table for storing key-value pairs
  • Dictionary (Python): Key-value pairs
    • del: Removes a key-value pair from a Python dictionary.
  • Map Methods (Java):
    • replace(): Replaces the value of a key in a Java Map.
    • get(): Retrieves the value associated with a key.
    • put(): Adds a key-value pair or replaces the value.

Heap Data Structures

  • Min Heap: Parent nodes are smaller than or equal to child nodes

  • Max Heap: Parent nodes are larger than or equal to child nodes

  • PriorityQueue (Java): Implements a priority queue; offer() enqueues, poll() dequeues the head.

  • Heap Methods (Java):

    • poll(): Removes and returns the head of the queue (lowest priority in a min-heap).
    • peek(): Retrieves the head without removing it.

  • PriorityQueue (Python): Use the queue library and the put() method to add. get() dequeues.

  • Heap Initialization (Java): new PriorityQueue() to create an empty priority queue.

  • PriorityQueue (Python): Use the heapq library to use a heap-based priority queue.

Other Data Structures

  • Set Initialization (Python): {"a", "b", "c"} initializes a set with the given values.
  • Sorted Order in Java: TreeSet ensures elements are stored in natural sorted order.
  • Insertion Order in Java: LinkedHashMap maintains insertion order. HashMaps do not.
  • Retrieving Keys (Java Map): keySet() retrieves all keys.
  • Removing (Del key name): del is used to delete items in dictionaries and lists in Python.

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