Array Insertion at End in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to insert a new element at the end of the array.

DSA C

arr[size] = [1];
size++;

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

Aarr[size]

Bsize

Cnew_element

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using size as the value instead of the new element.

Assigning to arr[size-1] which overwrites the last element.

We assign the new element to the position at the current size index, then increase size.

2fill in blank

medium

Complete the code to check if the array has space before insertion.

DSA C

if (size < [1]) {
    arr[size] = new_element;
    size++;
}

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

Anew_element

Bmax_size

Carr

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing size with arr instead of max_size.

Using new_element in the condition.

We compare size with max_size to ensure there is space to insert.

3fill in blank

hard

Fix the error in the insertion code to avoid overwriting elements.

DSA C

arr[[1]] = new_element;
size++;

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

Asize

Bsize - 1

C0

Dmax_size

Attempts:

3 left

💡 Hint

Common Mistakes

Using size - 1 which overwrites the last element.

Using max_size which is out of bounds.

Inserting at index size appends the element; size - 1 overwrites last element.

4fill in blank

hard

Fill both blanks to insert an element only if there is space.

DSA C

if ([1] < [2]) {
    arr[size] = new_element;
    size++;
}

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

Asize

Bmax_size

Cnew_element

Darr

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping size and max_size in the condition.

Using new_element or arr in the condition.

We check if size is less than max_size before inserting.

5fill in blank

hard

Fill all three blanks to insert and print the updated array size.

DSA C

if ([1] < [2]) {
    arr[[3]] = new_element;
    size++;
    printf("Size: %d\n", size);
}

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

Asize

Bmax_size

Dnew_element

Attempts:

3 left

💡 Hint

Common Mistakes

Using new_element as index.

Printing size before incrementing.

Check size < max_size, insert at arr[size], then increment size.

Practice

1. What happens when you insert an element at the end of an array in C if the array has enough space?

easy

A. The element is added at the last position and the array size increases by one.

B. The element replaces the first element of the array.

C. The array size remains the same and the element is ignored.

D. The array is sorted automatically after insertion.

Solution

1. Step 1: Understand array insertion at end

   When an element is inserted at the end, it is placed at the next free index if space is available.

2. Step 2: Effect on array size

   The logical size of the array increases by one because a new element is added.

3. Final Answer:

   The element is added at the last position and the array size increases by one. -> Option A

4. Quick Check:

   Insert at end adds element and increases size [OK]

Hint: Insert at end adds element at next free index [OK]

Common Mistakes:

• Thinking array size changes physically (fixed size in C)
• Assuming insertion replaces existing elements
• Believing array sorts automatically after insertion

2. Which of the following is the correct syntax to insert an element 'x' at the end of an array 'arr' with current size 'n' in C?

easy

A. arr[n+1] = x; n++;

B. arr[n] = x; n++;

C. arr[n-1] = x; n++;

D. arr[x] = n; n++;

Solution

1. Step 1: Identify correct index for insertion

   The next free position is at index 'n' since array indexing starts at 0 and current size is 'n'.

2. Step 2: Update size after insertion

   After inserting, increment 'n' to reflect the new size.

3. Final Answer:

   arr[n] = x; n++; -> Option B

4. Quick Check:

   Insert at arr[n], then increment n [OK]

Hint: Insert at arr[n], then increase size n [OK]

Common Mistakes:

• Using arr[n+1] causes out-of-bounds error
• Using arr[n-1] overwrites last element
• Confusing element and index positions

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

int arr[5] = {1, 2, 3};
int n = 3;
arr[n] = 4;
n++;
for(int i = 0; i < n; i++) {
    printf("%d ", arr[i]);
}

medium

A. 1 2 3 4

B. 1 2 3

C. 1 2 3 0

D. Compilation error

Solution

1. Step 1: Insert element at arr[3]

   arr[3] is assigned 4, so array becomes {1, 2, 3, 4, ?}.

2. Step 2: Increment size and print elements

   n becomes 4, loop prints arr[0] to arr[3]: 1 2 3 4.

3. Final Answer:

   1 2 3 4 -> Option A

4. Quick Check:

   Inserted 4 at end, printed all elements [OK]

Hint: Insert at arr[n], increment n, print up to n [OK]

Common Mistakes:

• Ignoring increment of n, printing only first 3 elements
• Assuming uninitialized arr[3] is zero
• Confusing array size and capacity

4. Find the error in the following code snippet that inserts an element at the end of an array:

int arr[5] = {10, 20, 30};
int n = 3;
arr[n+1] = 40;
n++;

medium

A. Array initialization is incorrect.

B. The size 'n' is not incremented correctly.

C. No error, code works fine.

D. The element is inserted at wrong index (arr[n+1] instead of arr[n]).

Solution

1. Step 1: Check insertion index

   Inserting at arr[n+1] means arr[4], skipping arr[3], which is incorrect for sequential insertion.

2. Step 2: Consequence of wrong index

   This causes a gap in the array; correct index is arr[n].

3. Final Answer:

   The element is inserted at wrong index (arr[n+1] instead of arr[n]). -> Option D

4. Quick Check:

   Insert at arr[n], not arr[n+1] [OK]

Hint: Insert at arr[n], not arr[n+1] to avoid errors [OK]

Common Mistakes:

• Using arr[n+1] instead of arr[n]
• Not updating size after insertion
• Ignoring array bounds

5. Given an array int arr[6] = {5, 10, 15, 20}; with current size n = 4, which code snippet correctly inserts the element 25 at the end and prints the updated array?

medium

A. arr[n-1] = 25; n++; for(int i=0; i

B. arr[n+1] = 25; n++; for(int i=0; i

C. arr[n] = 25; n++; for(int i=0; i

D. arr[5] = 25; n = 5; for(int i=0; i

Solution

1. Step 1: Identify correct insertion index

   Current size n=4 (indices 0-3 used), so end insertion at arr[4] (arr[n]), then n=5.

2. Step 2: Evaluate options

   A: arr[4]=25, n=5, prints 5 10 15 20 25 [correct].
   B: arr[5]=25, n=5, prints 0-4 (5 10 15 20 <uninit>) [misses 25].
   C: arr[3]=25 overwrites 20 [wrong].
   D: arr[5]=25, n=5, prints 0-4 [misses 25].

3. Final Answer:

   arr[n] = 25; n++; for(int i=0; i -> Option C

4. Quick Check:

   Insert at arr[n], n++, print 0 to n-1 [OK]

Hint: Insert at next free index, update size, print all elements [OK]

Common Mistakes:

• Inserting at wrong index causing overwrite
• Not updating size correctly
• Printing wrong number of elements