Two Pointer Technique on Arrays in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the left pointer to the start of the array.

DSA C

int left = [1];

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

A1

B-1

C0

Darray[0]

Attempts:

3 left

💡 Hint

Common Mistakes

Starting the pointer at 1 instead of 0.

Using the value of the first element instead of its index.

The left pointer should start at index 0 to point to the first element of the array.

2fill in blank

medium

Complete the code to initialize the right pointer to the end of the array.

DSA C

int right = [1] - 1;

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

Alen

Bsize

Carray_length

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using size instead of size - 1.

Using an undefined variable for array length.

The right pointer should start at the last index, which is size - 1.

3fill in blank

hard

Fix the error in the while loop condition to continue while left is less than right.

DSA C

while ([1] < right) {
    // loop body
}

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

Aright - 1

Bright

Cleft + 1

Dleft

Attempts:

3 left

💡 Hint

Common Mistakes

Using right < right which is always false.

Using left + 1 which is not a variable.

The loop should run while the left pointer is less than the right pointer.

4fill in blank

hard

Fill both blanks to move the left pointer forward and the right pointer backward.

DSA C

left[1];
right[2];

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

A++

B--

C+=

D-=

Attempts:

3 left

💡 Hint

Common Mistakes

Using -- for left pointer.

Using += or -= without a number.

Use ++ to move left forward and -- to move right backward by one.

5fill in blank

hard

Fill all three blanks to print the elements at left and right pointers and then move them.

DSA C

printf("%d %d\n", arr[1], arr[2]);
[3];
[4];

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

A[left]

B[right]

Cleft++

Dright--

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of brackets for array access.

Forgetting to move pointers after printing.

Print elements at arr[left] and arr[right], then increment left pointer and decrement right pointer.