Remove Duplicates from Sorted Array Two Pointer in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the slow pointer at the start of the array.

DSA C

int slow = [1];

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A0

B1

C-1

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Starting slow pointer at 1 instead of 0.

Using negative or out-of-bound indices.

The slow pointer starts at index 0 to track the position of unique elements.

2fill in blank

medium

Complete the code to move the fast pointer through the array.

DSA C

for (int fast = [1]; fast < n; fast++) {

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A-1

B1

Cn

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Starting fast pointer at 0 causing redundant comparisons.

Starting fast pointer at n causing out-of-bound errors.

The fast pointer starts at 1 to compare with the slow pointer at 0.

3fill in blank

hard

Fix the error in the condition to check if current element is different from last unique element.

DSA C

if (nums[fast] [1] nums[slow]) {

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A>=

B<=

C!=

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '!=' causing no duplicates to be removed.

Using '<=' or '>=' causing incorrect comparisons.

We check if the current element is not equal to the last unique element to identify duplicates.

4fill in blank

hard

Fill both blanks to update the slow pointer and assign the new unique element.

DSA C

slow[1];
nums[slow] = nums[2];

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A++

B--

C[fast]

D[slow]

Attempts:

3 left

💡 Hint

Common Mistakes

Decrementing slow pointer instead of incrementing.

Assigning nums[slow] to itself instead of nums[fast].

We increment slow by 1 and assign nums[fast] to nums[slow] to keep unique elements.

5fill in blank

hard

Fill in the blanks to return the count of unique elements after processing.

DSA C

return slow [1] [2];

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A+

B-

C1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Returning slow without adding 1 causing off-by-one error.

Subtracting 1 causing wrong count.

Adding 0 which does not change the value.

We return slow + 1 because slow is index-based, and adding 1 gives the count.