Why Two Pointer Technique Beats Brute Force in DSA C - Test Your Knowledge

Practice - 5 Tasks

1fill in blank

easy

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

DSA C

int left = [1];

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Aarray_length

B0

C-1

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Starting left pointer at 1 instead of 0.

Using array length as starting index.

The left pointer starts at index 0, the beginning of the array.

2fill in blank

medium

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

DSA C

int right = [1] - 1;

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Aarray_length

Barray_length + 1

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting right pointer to array_length (out of bounds).

Setting right pointer to 0.

The right pointer starts at the last index, which is array_length - 1.

3fill in blank

hard

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

DSA C

while ([1] < right) { /* process */ }

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Aright

Bleft + 1

C0

Dleft

Attempts:

3 left

💡 Hint

Common Mistakes

Using right < right in condition.

Using left + 1 < right which skips valid pairs.

The loop runs while the left pointer is less than the right pointer.

4fill in blank

hard

Fill both blanks to move pointers correctly based on sum comparison.

DSA C

if (sum < target) {
    [1]++;
} else {
    [2]--;
}

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Aleft

Bright

Csum

Dtarget

Attempts:

3 left

💡 Hint

Common Mistakes

Moving sum or target instead of pointers.

Moving pointers in wrong direction.

If sum is less than target, move left pointer forward to increase sum. Otherwise, move right pointer backward to decrease sum.

5fill in blank

hard

Fill the blanks to correctly handle sum comparisons, checking equality first.

DSA C

if (sum == target) {
    // found pair
} else if (sum [1] target) {
    [2]++;
} else {
    [3]--;
}

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

A<

Bleft

C>

Dright

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' in the else if.

Wrong pointer movements.

Check equality first. If sum < target, increment left to increase sum. Else (sum > target), decrement right to decrease sum.