Heap Concept Structure and Properties in DSA Rust - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an empty max heap using Rust's standard library.

DSA Rust

let mut heap = std::collections::BinaryHeap::[1]();

Drag options to blanks, or click blank then click option'

Afrom

Bdefault

Cwith_capacity

Dnew

Attempts:

3 left

💡 Hint

Common Mistakes

Using default() which also works but is less explicit here.

Using with_capacity() requires a size argument.

The new() function creates an empty BinaryHeap in Rust.

2fill in blank

medium

Complete the code to add an element 10 to the heap.

DSA Rust

heap.[1](10);

Drag options to blanks, or click blank then click option'

Ainsert

Bpush

Cadd

Denqueue

Attempts:

3 left

💡 Hint

Common Mistakes

Using insert() which is not a method of BinaryHeap.

Using add() or enqueue() which do not exist here.

The push() method adds an element to the BinaryHeap in Rust.

3fill in blank

hard

Fix the error in the code to remove the largest element from the heap.

DSA Rust

let max = heap.[1]();

Drag options to blanks, or click blank then click option'

Apop

Bremove

Cextract

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove() which requires an index and is not available.

Using extract() or delete() which do not exist.

The pop() method removes and returns the largest element from a max heap in Rust.

4fill in blank

hard

Fill both blanks to create a min heap by reversing the order of elements.

DSA Rust

use std::cmp::[1];
let mut min_heap = std::collections::BinaryHeap::new();
min_heap.push([2](5));

Drag options to blanks, or click blank then click option'

AReverse

BOrdering

CPartialOrd

DOrd

Attempts:

3 left

💡 Hint

Common Mistakes

Importing Ordering which is an enum, not a wrapper.

Using traits like PartialOrd or Ord directly.

Wrapping elements with Reverse makes the max heap behave like a min heap by reversing the comparison order.

5fill in blank

hard

Fill all three blanks to build a heap from a vector and pop the largest element.

DSA Rust

let data = vec![3, 1, 4];
let mut heap = std::collections::BinaryHeap::[1](data);
let largest = heap.[2]();
println!("Largest: {}", largest.[3]());

Drag options to blanks, or click blank then click option'

Afrom

Bpop

Cunwrap

Dnew

Attempts:

3 left

💡 Hint

Common Mistakes

Using new() which creates an empty heap.

Forgetting to unwrap the Option returned by pop.

BinaryHeap::from() builds a heap from a vector. pop() removes the largest element. unwrap() extracts the value from the Option.

Practice

1. What is the main property of a max-heap data structure?

easy

A. Every parent node is less than or equal to its children

B. Every parent node is greater than or equal to its children

C. All leaf nodes are at the same level

D. It is a balanced binary search tree

Solution

1. Step 1: Understand max-heap property

   A max-heap requires that each parent node's value is greater than or equal to its children.

2. Step 2: Compare options with definition

   Every parent node is greater than or equal to its children matches the max-heap property exactly; others describe different structures or properties.

3. Final Answer:

   Every parent node is greater than or equal to its children -> Option B

4. Quick Check:

   Max-heap property = parent ≥ children [OK]

Hint: Max-heap means parent is always bigger or equal [OK]

Common Mistakes:

• Confusing max-heap with min-heap property
• Thinking heap is a binary search tree
• Assuming all leaves are at the same level

2. Which of the following Rust code snippets correctly creates a max-heap using the standard library?

easy

A. let mut heap = std::collections::BinaryHeap::new();

B. let mut heap = std::collections::VecDeque::new();

C. let mut heap = std::collections::HashMap::new();

D. let mut heap = std::collections::BinaryHeap::new(0);

Solution

1. Step 1: Identify Rust heap creation syntax

   Rust's standard max-heap is created using BinaryHeap::new() for an empty heap.

2. Step 2: Check each option

   A: let mut heap = std::collections::BinaryHeap::new(); uses BinaryHeap::new(), which is correct. B: let mut heap = std::collections::VecDeque::new(); uses VecDeque (not a heap). C: uses HashMap (not a heap). D: uses BinaryHeap::new(0) which is invalid syntax since new() takes no arguments.

3. Final Answer:

   let mut heap = std::collections::BinaryHeap::new(); -> Option A

4. Quick Check:

   BinaryHeap::new() creates max-heap [OK]

Hint: Use BinaryHeap::new() to create max-heap in Rust [OK]

Common Mistakes:

• Using VecDeque or HashMap instead of BinaryHeap
• Confusing with capacity initialization
• Passing arguments to BinaryHeap::new()

3. What will be the output of the following Rust code using a max-heap?

use std::collections::BinaryHeap;

fn main() {
    let mut heap = BinaryHeap::new();
    heap.push(10);
    heap.push(5);
    heap.push(20);
    println!("{}", heap.pop().unwrap());
}

medium

A. 5

B. None

C. 10

D. 20

Solution

1. Step 1: Understand BinaryHeap behavior

   BinaryHeap in Rust is a max-heap by default, so pop() returns the largest element.

2. Step 2: Trace the pushed values and pop result

   Values pushed: 10, 5, 20. The largest is 20, so pop() returns 20.

3. Final Answer:

   20 -> Option D

4. Quick Check:

   Max-heap pop() returns max value 20 [OK]

Hint: pop() returns max value in Rust BinaryHeap [OK]

Common Mistakes:

• Thinking pop() returns smallest value
• Confusing push order with pop order
• Assuming pop() returns None if heap not empty

4. Identify the error in the following Rust code that tries to create a min-heap using BinaryHeap:

use std::collections::BinaryHeap;

fn main() {
    let mut heap = BinaryHeap::new();
    heap.push(3);
    heap.push(1);
    heap.push(2);
    println!("{}", heap.peek().unwrap());
}

medium

A. BinaryHeap is a max-heap by default, not min-heap

B. Missing import for min-heap

C. Cannot push integers into BinaryHeap

D. BinaryHeap does not support peek() method

Solution

1. Step 1: Check BinaryHeap default behavior

   Rust's BinaryHeap is a max-heap by default, so peek() returns the largest element, not the smallest.

2. Step 2: Identify why min-heap is not created

   The code pushes 3,1,2 but peek() returns 3 (max), not 1 (min). To create min-heap, a wrapper or Reverse is needed.

3. Final Answer:

   BinaryHeap is a max-heap by default, not min-heap -> Option A

4. Quick Check:

   BinaryHeap default = max-heap, not min-heap [OK]

Hint: BinaryHeap is max-heap by default; use Reverse for min-heap [OK]

Common Mistakes:

• Assuming peek() returns smallest element
• Thinking BinaryHeap can't store integers
• Believing peek() method is missing

5. You want to implement a priority queue in Rust that always returns the smallest element first. Which approach correctly achieves this using the standard library's BinaryHeap?

hard

A. Use Vec and sort it after every insertion

B. Use BinaryHeap directly as it is a min-heap by default

C. Use BinaryHeap with std::cmp::Reverse wrapper for elements

D. Use BinaryHeap and negate all values before pushing

Solution

1. Step 1: Understand BinaryHeap default behavior

   BinaryHeap is a max-heap by default, so it returns the largest element first.

2. Step 2: Find correct way to get min-heap behavior

   Wrapping elements with std::cmp::Reverse reverses ordering, making BinaryHeap behave like a min-heap.

3. Step 3: Evaluate other options

   Use BinaryHeap directly as it is a min-heap by default is wrong because BinaryHeap is max-heap by default. Use Vec and sort it after every insertion is inefficient. Use BinaryHeap and negate all values before pushing is a hack but not recommended.

4. Final Answer:

   Use BinaryHeap with std::cmp::Reverse wrapper for elements -> Option C

5. Quick Check:

   Reverse wrapper makes max-heap behave like min-heap [OK]

Hint: Wrap with Reverse to get min-heap from BinaryHeap [OK]

Common Mistakes:

• Assuming BinaryHeap is min-heap by default
• Sorting Vec after every insertion is inefficient
• Negating values is error-prone and not idiomatic