Merge Two Sorted Linked Lists in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new node with given value.

DSA C

struct Node* newNode(int data) {
    struct Node* node = (struct Node*)malloc(sizeof(struct Node));
    node->data = [1];
    node->next = NULL;
    return node;
}

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ANULL

Bnode

C0

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning NULL or 0 instead of the input data.

Using the node pointer instead of data.

The new node's data field should be set to the input parameter 'data'.

2fill in blank

medium

Complete the code to return the merged list head when one list is empty.

DSA C

struct Node* mergeSortedLists(struct Node* l1, struct Node* l2) {
    if (l1 == NULL) return [1];
    if (l2 == NULL) return l1;
    // merging logic continues...
}

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Al1

Bl2

Chead

DNULL

Attempts:

3 left

💡 Hint

Common Mistakes

Returning NULL instead of the other list.

Returning l1 when it is NULL.

If the first list is empty, return the second list as the merged result.

3fill in blank

hard

Fix the error in the comparison to choose the smaller node.

DSA C

if (l1->data [1] l2->data) {
    head = l1;
    head->next = mergeSortedLists(l1->next, l2);
} else {
    head = l2;
    head->next = mergeSortedLists(l1, l2->next);
}

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A>

B==

C<

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' which picks the larger node first.

Using '==' which only checks equality.

We pick the smaller node, so use '<' to compare data values.

4fill in blank

hard

Fill both blanks to complete the recursive merge function.

DSA C

struct Node* mergeSortedLists(struct Node* l1, struct Node* l2) {
    if (l1 == NULL) return [1];
    if (l2 == NULL) return [2];
    if (l1->data < l2->data) {
        l1->next = mergeSortedLists(l1->next, l2);
        return l1;
    } else {
        l2->next = mergeSortedLists(l1, l2->next);
        return l2;
    }
}

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Al2

Bl1

CNULL

Dhead

Attempts:

3 left

💡 Hint

Common Mistakes

Returning NULL instead of the other list.

Swapping the return values.

Return the other list when one is NULL: if l1 is NULL return l2, if l2 is NULL return l1.

5fill in blank

hard

Fill all three blanks to create a function that merges two sorted linked lists.

DSA C

struct Node* mergeSortedLists(struct Node* l1, struct Node* l2) {
    if (l1 == NULL) return [1];
    if (l2 == NULL) return [2];
    if (l1->data [3] l2->data) {
        l1->next = mergeSortedLists(l1->next, l2);
        return l1;
    } else {
        l2->next = mergeSortedLists(l1, l2->next);
        return l2;
    }
}

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

Al2

Bl1

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Returning NULL instead of the other list.

Using '>' instead of '<' in comparison.

Return the other list if one is NULL, and use '<' to pick the smaller node.