Array Deletion at Middle Index in DSA Rust - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the element at the middle index from the vector.

DSA Rust

let mut numbers = vec![1, 2, 3, 4, 5];
numbers.remove([1]);
println!("{:?}", numbers);

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

A2

B3

C1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 3 as the index which is out of middle range.

Using 1 or 0 which removes wrong elements.

The middle index of a vector with 5 elements is 2 (0-based index). Removing at index 2 removes the element 3.

2fill in blank

medium

Complete the code to find the middle index of the vector before removing the element.

DSA Rust

let mut nums = vec![10, 20, 30, 40, 50, 60];
let mid = nums.len() [1] 2;
nums.remove(mid);
println!("{:?}", nums);

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

A*

B-

C+

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' or '-' instead of division.

Using multiplication which increases the index.

To find the middle index, divide the length by 2 using the division operator '/'.

3fill in blank

hard

Fix the error in the code to correctly remove the middle element from the vector.

DSA Rust

let mut vals = vec![5, 10, 15, 20, 25];
let middle = vals.len() / 2;
vals.remove([1]);
println!("{:?}", vals);

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

Amiddle

Bvals.len()

Cmiddle + 1

Dmiddle - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Adding or subtracting 1 from middle causing wrong index.

Using length as index which is out of bounds.

The middle index is correctly calculated as length divided by 2. Use 'middle' directly to remove the middle element.

4fill in blank

hard

Fill both blanks to create a function that removes the middle element from any vector.

DSA Rust

fn remove_middle(vec: &mut Vec<i32>) {
    let mid = vec.len() [1] 2;
    vec.[2](mid);
}

let mut data = vec![7, 14, 21, 28, 35];
remove_middle(&mut data);
println!("{:?}", data);

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A/

Bremove

Cpop

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'pop' which removes last element instead of middle.

Using multiplication instead of division.

Divide length by 2 to find middle index, then call 'remove' method with that index to delete the middle element.

5fill in blank

hard

Fill both blanks to remove the middle element and return the updated vector.

DSA Rust

fn delete_middle(mut v: Vec<i32>) -> Vec<i32> {
    let mid = v.len() [1] 2;
    v.[2](mid);
    return v;
}

let numbers = vec![2, 4, 6, 8, 10];
let result = delete_middle(numbers);
println!("{:?}", result);

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

A/

Bremove

D.clone()

Attempts:

3 left

💡 Hint

Common Mistakes

Returning a clone instead of the modified vector.

Using incorrect operators or methods.

Divide length by 2 to find middle index, remove element at that index, and return the modified vector directly.

Practice

1. What happens when you delete the middle element from an array with an odd number of elements?

easy

A. The array size remains the same but the middle element is set to zero.

B. The middle element is removed and the array size decreases by one.

C. The last element is removed instead of the middle element.

D. The array is reversed after deletion.

Solution

1. Step 1: Identify the middle index in an odd-length array

   The middle index is calculated as length divided by 2 (integer division).

2. Step 2: Remove the element at the middle index

   Deleting this element reduces the array size by one and shifts elements after it left.

3. Final Answer:

   The middle element is removed and the array size decreases by one. -> Option B

4. Quick Check:

   Deleting middle element shrinks array [OK]

Hint: Middle index = length / 2 for odd arrays [OK]

Common Mistakes:

• Thinking array size stays the same after deletion
• Removing last element instead of middle
• Not shifting elements after deletion

2. Which Rust code snippet correctly deletes the middle element from a vector v with odd length?

easy

A. v.pop(v.len() / 2);

B. v.delete(v.len() / 2);

C. v.remove(v.len() / 2);

D. v.erase(v.len() / 2);

Solution

1. Step 1: Identify Rust method to remove element by index

   Rust's Vec type uses remove(index) to delete element at given index.

2. Step 2: Calculate middle index and call remove

   Middle index is v.len() / 2. Calling v.remove(v.len() / 2) deletes middle element.

3. Final Answer:

   v.remove(v.len() / 2); -> Option C

4. Quick Check:

   Use remove(index) to delete element [OK]

Hint: Use Vec::remove(index) to delete element [OK]

Common Mistakes:

• Using non-existent methods like delete or erase
• Using pop which removes last element only
• Passing index to pop which takes no arguments

3. What is the output of this Rust code?

let mut v = vec![10, 20, 30, 40, 50];
v.remove(v.len() / 2);
println!("{:?}", v);

medium

A. [10, 30, 40, 50]

B. [10, 20, 30, 40]

C. [20, 30, 40, 50]

D. [10, 20, 40, 50]

Solution

1. Step 1: Calculate middle index of vector

   Vector length is 5, so middle index = 5 / 2 = 2.

2. Step 2: Remove element at index 2 and print vector

   Element at index 2 is 30, removed. Remaining vector is [10, 20, 40, 50].

3. Final Answer:

   [10, 20, 40, 50] -> Option D

4. Quick Check:

   Removed middle element 30, vector shrinks [OK]

Hint: Remove element at len()/2 index for middle deletion [OK]

Common Mistakes:

• Removing wrong index element
• Confusing index with value
• Expecting vector size unchanged

4. Identify the error in this Rust code that tries to delete the middle element of a vector v:

let mut v = vec![1, 2];
v.remove(v.len() / 2 + 1);
println!("{:?}", v);

medium

A. Index used for removal is off by one, causing panic.

B. Vector cannot be mutable for removal.

C. remove() method does not exist for vectors.

D. The println! macro is used incorrectly.

Solution

1. Step 1: Calculate middle index for even-length vector

   Vector length is 2, middle index should be 2 / 2 = 1.

2. Step 2: Check removal index used in code

   Code uses index 1 + 1 = 2, which is out of bounds.

3. Step 3: Understand consequences

   Index 2 >= length 2 causes runtime panic (out of bounds).

4. Final Answer:

   Index used for removal is off by one, causing panic. -> Option A

5. Quick Check:

   Use correct middle index = len()/2 [OK]

Hint: Middle index is len()/2, no +1 for removal [OK]

Common Mistakes:

• Adding +1 to middle index incorrectly
• Trying to remove from immutable vector
• Misusing remove method name

5. Given a vector v of even length, how can you delete the lower middle element (the one at index len()/2 - 1) and then print the updated vector in Rust?

hard

A. v.remove(v.len() / 2 - 1); println!("{:?}", v);

B. v.remove(v.len() / 2); println!("{:?}", v);

C. v.pop(); println!("{:?}", v);

D. v.remove(v.len() / 2 + 1); println!("{:?}", v);

Solution

1. Step 1: Identify lower middle index for even-length vector

   For even length, lower middle index is len()/2 - 1.

2. Step 2: Remove element at lower middle index and print vector

   Use v.remove(v.len() / 2 - 1) to delete lower middle element, then print with println!("{:?}", v);.

3. Final Answer:

   v.remove(v.len() / 2 - 1); println!("{:?}", v); -> Option A

4. Quick Check:

   Remove lower middle with len()/2 - 1 [OK]

Hint: For even length, lower middle = len()/2 - 1 [OK]

Common Mistakes:

• Removing upper middle instead of lower middle
• Using pop which removes last element
• Adding +1 to index incorrectly