Longest Common Substring in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the maximum length variable to zero.

DSA C

int maxLen = [1];

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

A1

B0

C-1

DNULL

Attempts:

3 left

💡 Hint

Common Mistakes

Initializing maxLen to 1 causes incorrect results when no common substring exists.

Using NULL is invalid for integer initialization.

The maximum length of the common substring starts at zero before checking any characters.

2fill in blank

medium

Complete the code to update the DP table when characters match.

DSA C

if (s1[i - 1] == s2[j - 1]) {
    dp[i][j] = dp[i - 1][j - 1] [1] 1;
}

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

A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication causes wrong DP values.

Dividing dp values is not meaningful here.

When characters match, the length extends by 1 from the previous diagonal value.

3fill in blank

hard

Fix the error in updating the maximum length after DP update.

DSA C

if (dp[i][j] [1] maxLen) {
    maxLen = dp[i][j];
    endIndex = i - 1;
}

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

A<

B!=

C==

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' updates maxLen incorrectly.

Using '==' or '!=' does not update maxLen properly.

We update maxLen only if the current dp value is greater than maxLen.

4fill in blank

hard

Fill both blanks to correctly initialize the DP table with zeros.

DSA C

for (int i = 0; i <= len1; i++) {
    dp[i][[1]] = 0;
}
for (int j = 0; j <= len2; j++) {
    dp[[2]][j] = 0;
}

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

A0

Blen1

Dlen2

Attempts:

3 left

💡 Hint

Common Mistakes

Using len1 or len2 as indices causes out-of-bound errors.

Not initializing base cases leads to incorrect DP results.

The first row and first column of the DP table are initialized to zero to handle base cases.

5fill in blank

hard

Fill all three blanks to correctly extract the longest common substring from s1.

DSA C

int start = endIndex - [1] + 1;
char result[[2] + 1];
for (int i = 0; i < [3]; i++) {
    result[i] = s1[start + i];
}
result[[2]] = '\0';

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

AmaxLen

DendIndex

Attempts:

3 left

💡 Hint

Common Mistakes

Using endIndex instead of maxLen for length causes wrong substring size.

Not adding 1 for null terminator causes string errors.

We use maxLen to calculate the start index, allocate result size, and copy characters.