Merge Two Sorted Arrays Without Extra Space in DSA Rust - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to swap elements between two arrays.

DSA Rust

if arr1[i] > arr2[[1]] {
    let temp = arr1[i];
    arr1[i] = arr2[j];
    arr2[j] = temp;
}

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

Ai

Blen(arr2) - 1

C0

Dj

Attempts:

3 left

💡 Hint

Common Mistakes

Using i instead of j for arr2 index causes wrong element access.

Using 0 or len(arr2) - 1 ignores the current position in arr2.

We compare arr1[i] with arr2[j], so the index to access arr2 is j.

2fill in blank

medium

Complete the code to perform the final sorting of the first array.

DSA Rust

arr1.sort_by(|a, b| a[1]b);

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Acmp

Bpartial_cmp

Ceq

Dne

Attempts:

3 left

💡 Hint

Common Mistakes

Using eq or ne returns bool, not Ordering, causing compile errors.

Using partial_cmp returns Option, which is less direct.

The cmp method compares two values for sorting in Rust.

3fill in blank

hard

Fix the error in the loop condition to correctly iterate over arr1.

DSA Rust

for i in 0..[1] {
    // loop body
}

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Aarr2.len()

Barr1.len()

Carr1.len() - 1

Darr2.len() - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using arr2.len() causes index out of bounds if arr2 is smaller.

Using arr1.len() - 1 misses the last element.

We iterate over all elements of arr1, so use arr1.len() as the upper bound.

4fill in blank

hard

Fill both blanks to correctly swap and then sort both arrays.

DSA Rust

if arr1[[1]] > arr2[[2]] {
    let temp = arr1[i];
    arr1[i] = arr2[j];
    arr2[j] = temp;
}

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

Ai

Bj

C0

Dlen(arr2) - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 or len(arr2) - 1 ignores current indices.

Swapping with wrong indices causes incorrect order.

We compare arr1[i] and arr2[j], so use i and j as indices respectively.

5fill in blank

hard

Fill the blanks to complete the merge logic without extra space.

DSA Rust

let mut i = 0;
let mut j = 0;
while i < [1] && j < [2] {
    if arr1[i] > arr2[j] {
        let temp = arr1[i];
        arr1[i] = arr2[j];
        arr2[j] = temp;
        j += 1;
    } else {
        i += 1;
    }
}
arr1.sort();
arr2.sort();

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Aarr1.len()

Barr2.len()

Carr1.len() - 1

Darr2.len() - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using len() - 1 causes missing last element.

Using wrong array length causes index errors.

We loop while i < arr1.len() and j < arr2.len(), and increment j inside the loop.

Practice

1. What is the main goal when merging two sorted arrays without extra space?

easy

A. Sort each array separately using extra space

B. Combine both arrays into one sorted sequence without using extra memory

C. Copy elements from one array to another without sorting

D. Create a new array to hold merged elements

Solution

1. Step 1: Understand the problem requirement

   The problem asks to merge two sorted arrays into a sorted sequence without using extra space, meaning no new arrays can be created.

2. Step 2: Identify the correct approach

   We must rearrange elements within the given arrays to maintain sorted order combined, without additional memory.

3. Final Answer:

   Combine both arrays into one sorted sequence without using extra memory -> Option B

4. Quick Check:

   Merge without extra space = Combine in place [OK]

Hint: Merge by swapping elements, no new arrays needed [OK]

Common Mistakes:

• Trying to create a new array for merged result
• Sorting arrays separately without merging
• Ignoring the no extra space constraint

2. Which Rust syntax correctly declares two mutable sorted arrays for merging without extra space?

easy

A. let mut arr1 = [1, 3, 5]; let mut arr2 = [2, 4, 6];

B. let arr1 = [1, 3, 5]; let arr2 = [2, 4, 6];

C. mut arr1 = [1, 3, 5]; mut arr2 = [2, 4, 6];

D. let mut arr1 = (1, 3, 5); let mut arr2 = (2, 4, 6);

Solution

1. Step 1: Identify correct Rust mutable array declaration

   In Rust, arrays are declared with let mut for mutability and square brackets for arrays.

2. Step 2: Check each option

   let mut arr1 = [1, 3, 5]; let mut arr2 = [2, 4, 6]; uses let mut with arrays correctly. let arr1 = [1, 3, 5]; let arr2 = [2, 4, 6]; misses mut keyword. mut arr1 = [1, 3, 5]; mut arr2 = [2, 4, 6]; misses let keyword. let mut arr1 = (1, 3, 5); let mut arr2 = (2, 4, 6); uses tuples, not arrays.

3. Final Answer:

   let mut arr1 = [1, 3, 5]; let mut arr2 = [2, 4, 6]; -> Option A

4. Quick Check:

   Mutable arrays use let mut and [] [OK]

Hint: Use let mut and square brackets for mutable arrays [OK]

Common Mistakes:

• Forgetting mut keyword for mutable arrays
• Using tuples instead of arrays
• Missing let keyword

3. What will be the content of arrays after merging arr1 = [1, 4, 7] and arr2 = [2, 5, 6] without extra space using the gap method?

medium

A. ]7 ,6 ,5[ = 2rra ,]4 ,2 ,1[ = 1rra

B. arr1 = [1, 4, 5], arr2 = [2, 6, 7]

C. rr1 = [1, 2, 4], arr2 = [5, 6, 7]

D. arr1 = [1, 2, 4], arr2 = [5, 6, 7]

Solution

1. Step 1: Apply gap method to merge arrays

   Start with gap = ceil((3+3)/2) = 3. Compare and swap elements at gap distance across arrays until gap reduces to 0.

2. Step 2: Final arrays after merging

   After applying gap method, arr1 becomes [1, 2, 4] and arr2 becomes [5, 6, 7], maintaining sorted order without extra space.

3. Final Answer:

   arr1 = [1, 2, 4], arr2 = [5, 6, 7] -> Option D

4. Quick Check:

   Gap method merges arrays in place [OK]

Hint: Use gap method to compare and swap elements at decreasing gaps [OK]

Common Mistakes:

• Not reducing gap correctly
• Swapping elements incorrectly across arrays
• Confusing array indices during merge

4. Identify the error in this Rust code snippet for merging two sorted arrays without extra space:

let mut arr1 = [1, 5, 9];
let mut arr2 = [2, 6, 8];
for i in 0..arr1.len() {
    if arr1[i] > arr2[0] {
        let temp = arr1[i];
        arr1[i] = arr2[0];
        arr2[0] = temp;
    }
    arr2.sort();
}

medium

A. Using let temp causes ownership error in Rust

B. Swapping elements between arr1 and arr2 is not allowed

C. Sorting arr2 inside the loop is inefficient and incorrect

D. The loop range should be arr2.len() instead of arr1.len()

Solution

1. Step 1: Analyze the loop and sorting inside it

   The code sorts arr2 inside the loop for every iteration, which is inefficient and unnecessary.

2. Step 2: Correct approach for sorting arr2

   Sorting arr2 should be done once after all swaps, not inside the loop, to improve performance and correctness.

3. Final Answer:

   Sorting arr2 inside the loop is inefficient and incorrect -> Option C

4. Quick Check:

   Sort arr2 once after loop [OK]

Hint: Sort arr2 once after loop, not inside it [OK]

Common Mistakes:

• Sorting arr2 repeatedly inside loop
• Confusing loop ranges
• Misunderstanding Rust ownership with temp variable

5. Given two sorted arrays arr1 = [1, 3, 5, 7] and arr2 = [0, 2, 6, 8, 9], how can you merge them without extra space so that after merging, arr1 contains the first 4 smallest elements and arr2 contains the remaining elements sorted? Choose the correct final arrays.

hard

A. arr1 = [0, 1, 2, 3], arr2 = [5, 6, 7, 8, 9]

B. arr1 = [1, 2, 3, 5], arr2 = [0, 6, 7, 8, 9]

C. arr1 = [0, 1, 3, 5], arr2 = [2, 6, 7, 8, 9]

D. arr1 = [0, 1, 3, 6], arr2 = [2, 5, 7, 8, 9]

Solution

1. Step 1: Understand merging without extra space for unequal sizes

   We must rearrange elements so arr1 holds smallest 4 elements and arr2 holds the rest, both sorted.

2. Step 2: Apply gap method or swapping approach

   By comparing and swapping elements between arrays and sorting arr2, final arrays become arr1 = [0, 1, 2, 3] and arr2 = [5, 6, 7, 8, 9].

3. Final Answer:

   arr1 = [0, 1, 2, 3], arr2 = [5, 6, 7, 8, 9] -> Option A

4. Quick Check:

   First 4 smallest in arr1, rest in arr2 [OK]

Hint: Place smallest elements in arr1 by swapping, then sort arr2 [OK]

Common Mistakes:

• Not handling different array sizes correctly
• Failing to keep both arrays sorted after merge
• Assuming extra space is allowed