Palindrome Detection in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a string is a palindrome by comparing characters from start and end.

DSA C

int isPalindrome(char str[]) {
    int start = 0;
    int end = strlen(str) - 1;
    while (start < end) {
        if (str[start] != str[[1]]) {
            return 0;
        }
        start++;
        end--;
    }
    return 1;
}

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

Aend

Bstart

C0

Dstrlen(str)

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same index for both characters instead of start and end.

Comparing with a fixed index like 0 or length instead of 'end'.

We compare the character at the start index with the character at the end index to check for palindrome.

2fill in blank

medium

Complete the code to calculate the length of the string for palindrome check.

DSA C

int length = [1](str);

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Asize

Blength

Cstrlen

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using undefined functions like size or count.

Trying to use length as a function.

The strlen function returns the length of a string in C.

3fill in blank

hard

Fix the error in the palindrome check loop condition.

DSA C

while (start [1] end) {
    if (str[start] != str[end]) {
        return 0;
    }
    start++;
    end--;
}

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A>

B==

C<=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using equality or greater than which stops loop too early or causes errors.

Using less than or equal which may cause unnecessary comparisons.

The loop should continue while start is less than end to compare characters from both ends.

4fill in blank

hard

Fill both blanks to correctly reverse the string for palindrome comparison.

DSA C

int len = strlen(str);
char rev[len + 1];
for (int i = 0; i < len; i++) {
    rev[[1]] = str[[2]];
}
rev[len] = '\0';

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Alen - 1 - i

Bi

Clen + i

Di - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same index i for both strings which does not reverse.

Using incorrect index calculations causing out of bounds.

To reverse the string, assign rev[len - 1 - i] the character from str[i].

5fill in blank

hard

Fill all three blanks to create a function that returns 1 if palindrome, else 0.

DSA C

int isPalindrome(char str[]) {
    int start = 0;
    int end = [1](str) - 1;
    while (start [2] end) {
        if (str[start] != str[end]) {
            return [3];
        }
        start++;
        end--;
    }
    return 1;
}

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

Astrlen

B<

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong loop condition operators.

Returning 1 on mismatch instead of 0.

The function uses strlen to get length, loops while start < end, and returns 0 if mismatch found.