HashMap Implementation from Scratch in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare the size of the hash map array.

DSA C

const int TABLE_SIZE = [1];

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

A10

B1

C100

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using zero or one as table size causes no space or too small space.

The hash map array size is set to 10 to allow storing multiple entries with some space.

2fill in blank

medium

Complete the code to compute the hash index for a given key.

DSA C

unsigned int hash(char *key) {
    unsigned int hash = 0;
    for (int i = 0; key[i] != '\0'; i++) {
        hash += key[i];
    }
    return hash [1] TABLE_SIZE;
}

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

A*

B/

C%

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using division (/) can produce indices larger than TABLE_SIZE, causing out-of-bounds access.

The modulo operator (%) is used to keep the hash value within the table size range.

3fill in blank

hard

Fix the error in the insert function to correctly add a new key-value pair.

DSA C

void insert(HashMap *map, char *key, int value) {
    unsigned int index = hash(key);
    Entry *new_entry = malloc(sizeof(Entry));
    new_entry->key = key;
    new_entry->value = value;
    new_entry->next = map->table[[1]];
    map->table[index] = new_entry;
}

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

Amap

Bvalue

Ckey

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'value' or 'key' instead of the index causes wrong memory access.

The new entry's next pointer should point to the current head at the computed index, so use 'index' to access the correct bucket.

4fill in blank

hard

Fill both blanks to complete the search function that finds a value by key.

DSA C

int search(HashMap *map, char *key) {
    unsigned int index = hash(key);
    Entry *current = map->table[[1]];
    while (current != NULL) {
        if (strcmp(current->key, [2]) == 0) {
            return current->value;
        }
        current = current->next;
    }
    return -1;
}

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

Aindex

Bkey

Cmap

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variables for bucket or key comparison.

The search starts at the bucket at 'index' and compares each entry's key with the given 'key'.

5fill in blank

hard

Fill all three blanks to complete the delete function that removes a key from the map.

DSA C

void delete(HashMap *map, char *key) {
    unsigned int index = hash(key);
    Entry *current = map->table[index];
    Entry *prev = NULL;
    while (current != NULL) {
        if (strcmp(current->key, [1]) == 0) {
            if ([2] == NULL) {
                map->table[index] = current->next;
            } else {
                [3]->next = current->next;
            }
            free(current);
            return;
        }
        prev = current;
        current = current->next;
    }
}

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

Akey

Bprev

Dcurrent

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variables for key comparison or pointer updates.

The function compares keys, checks if the previous entry is NULL to update the head, otherwise links previous to next.