Character Frequency Counting in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an array to store frequency of all ASCII characters.

DSA C

int freq[[1]] = {0};

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A64

B256

C512

D128

Attempts:

3 left

💡 Hint

Common Mistakes

Using 128 instead of 256, which misses extended ASCII characters.

Using too small or too large array size.

The ASCII table has 256 characters, so we need an array of size 256 to store frequency counts.

2fill in blank

medium

Complete the code to increment the frequency count of the current character in the string.

DSA C

freq[(unsigned char)[1]]++;

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Astr[i]

Bi

Cch

Dc

Attempts:

3 left

💡 Hint

Common Mistakes

Using the index variable i directly instead of the character.

Using an undefined variable.

We use str[i] to access the current character in the string and increment its frequency.

3fill in blank

hard

Fix the error in the loop condition to iterate over the string until the end.

DSA C

for (int i = 0; str[i] [1] '\0'; i++) {

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A==

B>

C<

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' which stops immediately.

Using '<' or '>' which is invalid for char comparison here.

The loop should continue while the current character is not the null terminator '\0'.

4fill in blank

hard

Fill both blanks to print characters and their frequencies only if frequency is greater than zero.

DSA C

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

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A256

B>

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Looping less than 256 characters.

Checking frequency with '==' instead of '>'.

We loop through all 256 ASCII characters and print only those with frequency greater than zero.

5fill in blank

hard

Fill all three blanks to create a function that counts character frequency and prints the result.

DSA C

void countFrequency(const char *[1]) {
    int freq[[2]] = {0};
    for (int i = 0; [3][i] != '\0'; i++) {
        freq[(unsigned char)[3][i]]++;
    }
    for (int i = 0; i < 256; i++) {
        if (freq[i] > 0) {
            printf("%c: %d\n", i, freq[i]);
        }
    }
}

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

Astr

B256

Dinput

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

Wrong array size.

Incorrect loop variable.

The function takes a string named 'str', uses an array of size 256, and loops over 'str' to count frequencies.