Minimum Window Substring in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the left pointer for the sliding window.

DSA C

int left = [1];

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

A0

B1

C-1

Ds.length

Attempts:

3 left

💡 Hint

Common Mistakes

Starting left pointer at 1 instead of 0.

Using negative index which is invalid.

The left pointer starts at index 0 to begin scanning the string from the start.

2fill in blank

medium

Complete the code to check if the current character is in the target frequency map.

DSA C

if (target_freq[s[right]] [1] 0) {

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

A==

B<

C!=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' which only checks equality, not presence.

Using '<' which is incorrect for frequency check.

We check if the frequency of the character is greater than zero to know if it is needed.

3fill in blank

hard

Fix the error in the condition to shrink the window when all characters are matched.

DSA C

while (formed [1] required) {

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

A==

B<

C>

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' which causes incorrect shrinking.

Using '<' or '>' which do not represent the correct condition.

We shrink the window only when the number of formed characters equals the required count.

4fill in blank

hard

Fill both blanks to update the minimum window size and start index.

DSA C

if (right - left + 1 [1] min_len) {
    min_len = right - left + 1;
    min_start = [2];
}

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

A<

B>

Cleft

Dright

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' causes wrong window size update.

Setting min_start to right instead of left.

We update min_len if the current window is smaller and record the start index as left.

5fill in blank

hard

Fill all three blanks to correctly update the frequency map and formed count when shrinking the window.

DSA C

char c = s[left];
window_freq[c]--;
if (window_freq[c] [1] target_freq[c]) {
    formed [2];
}
left [3] 1;

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

A<

B--

C+

D++

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' in frequency comparison.

Incrementing formed instead of decrementing.

Moving left pointer backward instead of forward.

When the window frequency falls below target, formed decreases; left pointer moves right.