Array Deletion at End in DSA Java - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the last element from the array by decreasing the size.

DSA Java

if (size > 0) {
    size = size [1] 1;
}

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

A+

B/

C-

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' instead of '-' to change size.

Trying to multiply or divide size.

To delete the last element, we reduce the size by 1 using the minus operator.

2fill in blank

medium

Complete the code to check if the array is empty before deletion.

DSA Java

if ([1] > 0) {
    size--;
}

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

Acapacity

Bindex

Carray.length

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Checking capacity or array length instead of size.

Using an undefined variable like index.

We check if 'size' is greater than zero to ensure there is an element to delete.

3fill in blank

hard

Fix the error in the deletion method to correctly update the size.

DSA Java

public void deleteLast() {
    if (size > 0) {
        size [1] 1;
    }
}

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

A-=

B/=

C*=

D+=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+=' which increases size.

Using '*=' or '/=' which are incorrect here.

The size should be decreased by 1 using the '-=' operator to delete the last element.

4fill in blank

hard

Fill both blanks to correctly check and delete the last element.

DSA Java

if ([1] > 0) {
    [2]--;
}

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

Asize

Bcapacity

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using capacity or index instead of size.

Decrementing the wrong variable.

We check if size > 0 and then decrease size by 1 to delete the last element.

5fill in blank

hard

Fill all three blanks to implement a safe deleteLast method.

DSA Java

public void deleteLast() {
    if ([1] > 0) {
        [2] [3] 1;
    }
}

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

Asize

B-=

D+=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+=' instead of '-='.

Checking or updating wrong variables.

Check if size > 0, then reduce size by 1 using '-=' operator on size.

Practice

1. What happens when you delete an element from the end of a fixed-size array in Java?

easy

A. The last element is removed and the array size decreases by one

B. The last element is set to zero or null but the array size stays the same

C. All elements shift left by one position

D. The array is completely cleared

Solution

1. Step 1: Understand fixed-size array behavior

   Java arrays have a fixed size once created, so their length cannot change.

2. Step 2: Effect of deleting at end

   Deleting means logically ignoring the last element or setting it to default (0 or null), but the array length remains unchanged.

3. Final Answer:

   The last element is set to zero or null but the array size stays the same -> Option B

4. Quick Check:

   Fixed-size array length unchanged on deletion [OK]

Hint: Fixed arrays keep size; deletion just clears last element [OK]

Common Mistakes:

• Thinking array size shrinks automatically
• Assuming elements shift after deletion
• Believing array clears fully on one deletion

2. Which of the following is the correct syntax to delete the last element from an array named arr in Java by reducing its logical size stored in size?

easy

A. arr[size--] = 0;

B. arr[size] = 0; size--;

C. size--; arr[size] = 0;

D. arr[size] = null; size++;

Solution

1. Step 1: Understand logical deletion

   To delete last element, first reduce size by one, then clear that element.

2. Step 2: Check syntax correctness

   size--; arr[size] = 0; reduces size first (size--) then sets arr[size] to 0, correctly deleting last element.

3. Final Answer:

   size--; arr[size] = 0; -> Option C

4. Quick Check:

   Decrease size before clearing element [OK]

Hint: Decrease size first, then clear element [OK]

Common Mistakes:

• Clearing element before decreasing size
• Using post-decrement incorrectly
• Increasing size instead of decreasing

3. What will be the output of the following Java code?

int[] arr = {10, 20, 30, 40, 50};
int size = 5;
size--;
arr[size] = 0;
for(int i = 0; i < size; i++) {
    System.out.print(arr[i] + " ");
}

medium

A. 10 20 30 0 0

B. 10 20 30 40 0

C. 10 20 30 40 50

D. 10 20 30 40

Solution

1. Step 1: Understand size decrement and element clearing

   Size is reduced from 5 to 4, then arr[4] is set to 0, removing last element logically.

2. Step 2: Loop prints elements from index 0 to 3

   Loop runs i=0 to 3, printing arr[0]=10, arr[1]=20, arr[2]=30, arr[3]=40.

3. Final Answer:

   10 20 30 40 -> Option D

4. Quick Check:

   Last element removed, loop prints first 4 elements [OK]

Hint: Loop runs till size, last element skipped after decrement [OK]

Common Mistakes:

• Printing all 5 elements ignoring size
• Not updating last element to zero
• Confusing array index with size

4. Identify the error in this Java code snippet that tries to delete the last element from an array:

int[] arr = {1, 2, 3, 4};
int size = 4;
arr[size] = 0;
size--;

medium

A. Array index out of bounds error at arr[size] = 0;

B. Size variable is not decremented

C. Array elements are not shifted left

D. No error, code works fine

Solution

1. Step 1: Check array indexing

   Array indices go from 0 to size-1, so arr[size] is out of bounds.

2. Step 2: Identify correct order

   Must decrement size first, then access arr[size] to avoid error.

3. Final Answer:

   Array index out of bounds error at arr[size] = 0; -> Option A

4. Quick Check:

   Accessing arr[size] causes error [OK]

Hint: Decrement size before accessing arr[size] [OK]

Common Mistakes:

• Accessing arr[size] directly
• Not decrementing size before deletion
• Ignoring array index limits

5. You have an array int[] arr = {5, 10, 15, 20, 25} and a variable size = 5. You want to logically delete the last two elements without modifying the values in the array and print the remaining elements. Which code snippet correctly does this?

hard

A. size -= 2;
for(int i = 0; i < size; i++) System.out.print(arr[i] + " ");

B. arr[size-1] = 0; arr[size-2] = 0; size -= 2;
for(int i = 0; i < size; i++) System.out.print(arr[i] + " ");

C. size -= 2;
arr[size] = 0; arr[size+1] = 0;
for(int i = 0; i < size; i++) System.out.print(arr[i] + " ");

D. for(int i = 0; i < size-2; i++) System.out.print(arr[i] + " ");

Solution

1. Step 1: Reduce logical size by 2

   Decreasing size by 2 means last two elements are ignored logically.

2. Step 2: Print elements up to new size

   Loop from 0 to size-1 prints remaining elements correctly.

3. Final Answer:

   size -= 2; for(int i = 0; i < size; i++) System.out.print(arr[i] + " "); -> Option A

4. Quick Check:

   Logical size controls printed elements [OK]

Hint: Reduce size, then print up to size [OK]

Common Mistakes:

• Setting elements to zero before reducing size
• Printing without adjusting size
• Accessing invalid indices after deletion