First Non Repeating Character Using Hash in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare the frequency array for all ASCII characters.

DSA C

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

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A256

B64

C128

D512

Attempts:

3 left

💡 Hint

Common Mistakes

Using 128 instead of 256 causes out-of-bound errors for extended ASCII characters.

The frequency array size should be 256 to cover all ASCII characters.

2fill in blank

medium

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

DSA C

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

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Aindex

Bj

Ck

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable not declared or not used in the loop.

The loop variable 'i' is used to access each character in the string.

3fill in blank

hard

Fix the error in the loop condition to find the first non-repeating character.

DSA C

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

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Ak

Bj

Ci

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variables in initialization and condition causes errors.

The loop variable should be 'i' to match the condition and increment.

4fill in blank

hard

Fill both blanks to check if the character frequency is 1 and return it.

DSA C

if (freq[(unsigned char)str[[1]]] [2] 1) {
    return str[i];
}

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Ai

B==

C!=

Dj

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' instead of '==' causes wrong character to be returned.

We check if the frequency of the character at index 'i' is equal to 1.

5fill in blank

hard

Fill all three blanks to complete the function that returns the first non-repeating character or '_' if none found.

DSA C

char firstNonRepeatingChar(char *str) {
    int freq[[1]] = {0};
    for (int [2] = 0; str[[2]] != '\0'; [2]++) {
        freq[(unsigned char)str[[2]]]++;
    }
    for (int i = 0; str[i] != '\0'; i++) {
        if (freq[(unsigned char)str[i]] [3] 1) {
            return str[i];
        }
    }
    return '_';
}

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

A256

Bi

C==

Dj

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong array size, wrong loop variable, or wrong comparison operator.

The frequency array size is 256, the loop variable is 'i', and the frequency check uses '=='.