String Traversal and Character Access in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print each character of the string using a loop.

DSA C

char str[] = "hello";
for (int i = 0; i < [1]; i++) {
    printf("%c\n", str[i]);
}

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

Astr.length

B5

Cstrlen(str)

Dsizeof(str)

Attempts:

3 left

💡 Hint

Common Mistakes

Using sizeof(str) which includes the null terminator and size of array.

Using a fixed number without considering string length.

strlen(str) returns the length of the string excluding the null character, so the loop prints all characters.

2fill in blank

medium

Complete the code to access the last character of the string.

DSA C

char str[] = "world";
char last_char = str[[1]];
printf("%c\n", last_char);

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Astrlen(str) - 1

Bsizeof(str) - 1

Cstrlen(str)

Dsizeof(str)

Attempts:

3 left

💡 Hint

Common Mistakes

Using strlen(str) as index which is out of bounds.

Using sizeof(str) which includes null terminator.

The last character is at index length - 1 because indexing starts at 0.

3fill in blank

hard

Fix the error in the code to correctly print characters until the null terminator.

DSA C

char str[] = "test";
int i = 0;
while (str[[1]] != '\0') {
    printf("%c\n", str[i]);
    i++;
}

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Astrlen(str)

B0

C1

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using a fixed index like 0 or 1 in the condition causes infinite loop or wrong output.

Using strlen(str) inside the condition without updating index.

The loop should check str[i] to stop at the null terminator correctly.

4fill in blank

hard

Fill both blanks to create a loop that prints characters only if they are vowels.

DSA C

char str[] = "example";
for (int i = 0; i < [1]; i++) {
    if (str[i] == [2]) {
        printf("%c\n", str[i]);
    }
}

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Astrlen(str)

B'a'

C'e'

D'x'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong loop limit causing out of bounds.

Checking for a consonant instead of a vowel.

Loop runs through the string length and prints characters only if they are 'e' (a vowel).

5fill in blank

hard

Fill all three blanks to create a loop that counts how many times 'l' appears in the string.

DSA C

char str[] = "hello world";
int count = 0;
for (int i = 0; i < [1]; i++) {
    if (str[i] == [2]) {
        [3];
    }
}
printf("%d\n", count);

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Astrlen(str)

B'l'

Ccount++

Di++

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong character in condition.

Not incrementing count inside if block.

Loop runs through the string length, checks if character is 'l', and increments count.