# C Programming Exercises, Practice, Solution : Linked List

## C Singly Linked List [42 exercises with solution]

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1. Write a program in C to create and display a Singly Linked List.
Test Data :
Input the number of nodes : 3
Input data for node 1 : 5
Input data for node 2 : 6
Input data for node 3 : 7
Expected Output :

``` Data entered in the list :
Data = 5
Data = 6
Data = 7
```

Click me to see the solution

2. Write a program in C to create a singly linked list of n nodes and display it in reverse order.
Test Data :
Input the number of nodes : 3
Input data for node 1 : 5
Input data for node 2 : 6
Input data for node 3 : 7
Expected Output :

``` Data entered in the list are :
Data = 5
Data = 6
Data = 7

The list in reverse are :
Data = 7
Data = 6
Data = 5
```

Click me to see the solution

3. Write a program in C to create a singly linked list of n nodes and count the number of nodes.
Test Data :
Input the number of nodes : 3
Input data for node 1 : 5
Input data for node 2 : 6
Input data for node 3 : 7
Expected Output :

``` Data entered in the list are :
Data = 5
Data = 6
Data = 7

Total number of nodes = 3
```

Click me to see the solution

4. Write a program in C to insert a new node at the beginning of a Singly Linked List.
Test Data and Expected Output :

``` Input the number of nodes : 3
Input data for node 1 : 5
Input data for node 2 : 6
Input data for node 3 : 7

Data entered in the list are :
Data = 5
Data = 6
Data = 7

Input data to insert at the beginning of the list : 4

Data after inserted in the list are :
Data = 4
Data = 5
Data = 6
Data = 7
```

Click me to see the solution

5. Write a program in C to insert a new node at the end of a Singly Linked List.
Test Data and Expected Output :

```Input the number of nodes : 3
Input data for node 1 : 5
Input data for node 2 : 6
Input data for node 3 : 7

Data entered in the list are :
Data = 5
Data = 6
Data = 7

Input data to insert at the end of the list : 8

Data, after inserted in the list are :
Data = 5
Data = 6
Data = 7
Data = 8
```

Click me to see the solution

6. Write a program in C to insert a node in the middle of a Singly Linked List.
Test Data and Expected Output :

```Input the number of nodes (3 or more) : 4
Input data for node 1 : 1
Input data for node 2 : 2
Input data for node 3 : 3
Input data for node 4 : 4

Data entered in the list are :
Data = 1
Data = 2
Data = 3
Data = 4

Input data to insert in the middle of the list : 5
Input the position to insert new node : 3

Insertion completed successfully.

The new list are :
Data = 1
Data = 2
Data = 5
Data = 3
Data = 4
```

Click me to see the solution

7. Write a program in C to delete the first node of a Singly Linked List.
Test Data :
Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 3
Input data for node 3 : 4
Expected Output :

``` Data entered in the list are :
Data = 2
Data = 3
Data = 4

Data of node 1 which is being deleted is :  2

Data, after deletion of first node :
Data = 3
Data = 4
```

Click me to see the solution

8. Write a program in C to delete a node from the middle of a Singly Linked List.
Test Data and Expected Output :

```Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8

Data entered in the list are :
Data = 2
Data = 5
Data = 8

Input the position of node to delete : 2

Deletion completed successfully.

The new list are  :
Data = 2
Data = 8
```

Click me to see the solution

9. Write a program in C to delete the last node of a Singly Linked List.
Test Data :
Input the number of nodes : 3
Input data for node 1 : 1
Input data for node 2 : 2
Input data for node 3 : 3
Expected Output :

``` Data entered in the list are :
Data = 1
Data = 2
Data = 3

The new list after deletion the last node are  :
Data = 1
Data = 2
```

Click me to see the solution

10. Write a program in C to search for an existing element in a singly linked list.
Test Data and Expected Output :

```Input the number of nodes : 3

Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8

Data entered in the list are :
Data = 2
Data = 5
Data = 8

Input the element to be searched : 5
Element found at node 2
```

Click me to see the solution

11. Write a C program that converts a singly linked list into a string and returns it.
Test Data and Expected Output :

```
-------------------------------------------------------------
Input the number of nodes: 3
Input data for node 1 : 10
Input data for node 2 : 20
Input data for node 3 : 30

Return data entered in the list as a string:
The linked list: 10 20 30
```

Click me to see the solution

12. Write a C program that converts a singly linked list into an array and returns it.
Test Data and Expected Output :

```
-------------------------------------------------------------
Input the number of nodes: 3
Input data for node 1 : 10
Input data for node 2 : 20
Input data for node 3 : 30

Return data entered in the list as a string:
The linked list: 10 20 30
```

Click me to see the solution

13. Write a C program to merge two sorted singly linked lists into a single sorted linked list.
Test Data and Expected Output :

```Two sorted singly linked lists:
1 3 5 7
2 4 6

After merging the said two sorted lists:
1 2 3 4 5 6 7
```

Click me to see the solution

14. Write a C program to detect and remove a loop in a singly linked list.
Test Data and Expected Output :

```Original singly linked list:
1 2 3 4 5

Create the loop:
Following statement display the loop:

After removing the said loop:
1 2 3 4 5
```

Click me to see the solution

15. Write a C program to check if a singly linked list is a palindrome or not.
Test Data and Expected Output :

```Original Singly List:
1 2 3 4 5
Linked list is not a palindrome.

Original Singly List:
1 2 2 1

Original Singly List:
```

Click me to see the solution

16. Write a C program to remove duplicates from a single unsorted linked list.
Test Data and Expected Output :

```Original Singly List:
1 2 3 3 4
After removing duplicate elements from the said singly list:
1 2 3 4

Original Singly List:
1 2 3 3 4 4
After removing duplicate elements from the said singly list:
1 2 3 4
```

Click me to see the solution

17. Write a C program to sort a singly linked list using merge sort.
Test Data and Expected Output :

```Sort the said singly linked list using merge sort:
2 3 1 7 5

After sorting the said list:
1 2 3 5 7
```

Click me to see the solution

18. Write a C program to create a copy of a singly linked list with random pointers.
Test Data and Expected Output :

```Original singly list:
1 2 3 5 7

After setting the random pointers:
Data: 1, Random: 3
Data: 2, Random: 5
Data: 3, Random: 7
Data: 5, Random: 1
Data: 7, Random: 3
```

Click me to see the solution

19. Write a C program to find the intersection of two singly linked lists.
Test Data and Expected Output :

```Original lists:
1 2 3 4
5 3 4
Intersection found at 3.

Original lists:
1 2 3 4
5 3 4
```

Click me to see the solution

20. Write a C program to get the n number of nodes from the end of a singly linked list.
Test Data and Expected Output :

```Original list:
1 3 5 11
Last 2 nodes from the end of the said singly list:
5 11
Last 3 nodes from the end of the said singly list:
3 5 11
Last 4 nodes from the end of the said singly list:
1 3 5 11
Last 1 node from the end of the said singly list:
11
Last 5 node from the end of the said singly list:
```

Click me to see the solution

21. Write a C program to partition a singly linked list based on a specific value.
Test Data and Expected Output:

```Original list:
3 5 7 5 9 2 1
Linked List after partition around 5:
3 2 1 5 7 5 9
```

Click me to see the solution

22. Write a C program that takes two linked lists of numbers. Each node contains a single digit and returns the sum of those numbers of said linked lists as a linked list.
Test Data and Expected Output :

```List-1
8 7 9 2
List-2
2 1 2 3

0 9 1 6
```

Click me to see the solution

23. Write a C program that rotates a singly linked list to the right by k places.
Test Data and Expected Output :

```Original List: 1 3 4 7 9

Rotate the said singly linked list to the right by 1 places:
9 1 3 4 7

Rotate the said singly linked list to the right by 2 places:
4 7 9 1 3

Rotate the said singly linked list to the right by 4 places:
7 9 1 3 4
```

Click me to see the solution

24. Write a C program to swap Kth node from the beginning with Kth node from the end in a singly linked list.
Test Data and Expected Output :

```Original List: 1 3 4 7 9

Rotate the said singly linked list to the right by 1 places:
9 1 3 4 7

Rotate the said singly linked list to the right by 2 places:
4 7 9 1 3

Rotate the said singly linked list to the right by 4 places:
7 9 1 3 4
```

Click me to see the solution

25. Write a C program that removes elements with odd indices from a singly linked list.
Test Data and Expected Output :

```Original linked list:
7 6 5 4 3 2 1

Linked list after removing odd indices:
6 4 2
```

Click me to see the solution

26. Write a C program that removes elements with even indices from a singly linked list.
Test Data and Expected Output :

```Original linked list:
7 6 5 4 3 2 1

Linked list after removing even indices:
6 4 2
```

Click me to see the solution

27. Write a C program to implement a binary tree using linked list representation.
Test Data and Expected Output :

```Traversal of a binary tree:
40 20 50 10 30
```

Click me to see the solution

28. Write a C program to remove the Nth node from the end of a singly linked list.
Test Data and Expected Output :

```Original Singly List:
1 2 3 4 5

Remove 1st node from the end of a singly linked list:
1 2 3 4

Remove 3rd node from the end of a singly linked list:
1 3 4
```

Click me to see the solution

29. Write a C program to merge k sorted linked lists into a single sorted linked list.
Test Data and Expected Output :

```List-1:
10 20 50
List-2:
30 40 60
List-3:
10 70 100

After merging the said three sorted lists into one sorted list:
10 10 20 30 40 50 60 70 100
```

Click me to see the solution

30. Write a C program to create and reorder a linked list placing all even-numbered nodes ahead of all odd-numbered nodes.
Test Data and Expected Output :

```Original Singly List:
1 2 3 4 5 6

Reorder the said linked list placing all even-numbered
nodes ahead of all odd-numbered nodes:
1 3 5 2 4 6
```

Click me to see the solution

31. Write a C program to reverse a singly linked list in pairs.
Test Data and Expected Output :

```Original List: 1 2 3 4 5 6
Reverse a singly linked list in pairs:
2 1 4 3 6 5

Original List: 1 2 3 4 5
Reverse a singly linked list in pairs:
2 1 4 3 5
```

Click me to see the solution

32. Write a C program to split a singly linked list into two halves.
Test Data and Expected Output :

```Original List: 1 2 3 4 5
Split the said singly linked list into halves:
First half: 1 2 3
Second half: 4 5

Original List: 1 2 3 4 5 6
Split the said singly linked list into halves:
First half: 1 2 3
Second half: 4 5 6
```

Click me to see the solution

33. Write a C program to delete alternate nodes of a singly linked list.
Test Data and Expected Output :

```Original List:
1 2 3 4 5 6 7

Delete alternate nodes of the said singly linked list:
1 3 5 7
```

Click me to see the solution

34. Write a C program to to merge alternate nodes of two singly linked lists.
Test Data and Expected Output :

```First linked list: 9 7 5 3 1
Second linked list: 10 8 6 4 2
Merged linked list: 9 10 7 8 5 6 3 4 1 2
```

Click me to see the solution

35. Write a C program to remove duplicates from a sorted singly linked list.
Test Data and Expected Output :

```Original sorted singly linked list:
1 2 3 3 5 6 6

After removing duplicates from the said sorted linked list:
1 2 3 5 6
```

Click me to see the solution

36. Write a C program to reverse a singly linked list starting at the first position in blocks of size k.
Test Data and Expected Output :

```Given linked list:
1 2 3 4 5 6 7 8
Reverse the first 3 nodes of the said Linked list:
3 2 1 6 5 4 8 7
Reverse the first 5 nodes of the said Linked list:
5 6 1 2 3 7 8 4
```

Click me to see the solution

37. Write a C program to remove all elements from a singly linked list that are greater than a given value x.
Test Data and Expected Output :

```Given linked list:
1 2 3 4 5 6 7 8
Reverse the first 3 nodes of the said Linked list:
3 2 1 6 5 4 8 7
Reverse the first 5 nodes of the said Linked list:
5 6 1 2 3 7 8 4
```

Click me to see the solution

38. Write a C program to find a pair in a singly linked list whose sum is equal to a given value.
Test Data and Expected Output :

```Original singly linked list:
1 2 3 4 5 6 7

Find a pair whose sum is equal to 4:
(1,3)

Find a pair whose sum is equal to 11:
(4,7) (5,6)

Find a pair whose sum is equal to 5:
(1,4) (2,3)

Find a pair whose sum is equal to 14:
```

Click me to see the solution

39. Write a C program to interleave elements of two singly linked lists alternatively.
Test Data and Expected Output :

```Original Lists:
List1: 1 3 5 7
List2: 2 4 6 8

After interleaving the two linked lists alternatively:
List1: 1 2 3 4 5 6 7 8
List2: 2 3 4 5 6 7 8
```

Click me to see the solution

40. Write a C program to swap every two adjacent nodes of a given singly linked list.
Test Data and Expected Output :

```Original List:
1 2 3 4 5

Updated List after swapping every two adjacent nodes:
2 1 4 3 5
```

Click me to see the solution

41. Write a C program to reverse alternate k nodes of a given singly linked list.
Test Data and Expected Output :

```Original List: 1 2 3 4 5 6 7 8

Reverse alternate k (k=2) nodes of the said singly linked list:
2 1 3 4 6 5 7 8

Reverse alternate k (k=3) nodes of the said singly linked list:
3 1 2 4 6 5 8 7

Reverse alternate k (k=4) nodes of the said singly linked list:
4 2 1 3 6 5 8 7

```

Click me to see the solution

42. Write a C program to find the point at which two singly linked lists intersect.
Test Data and Expected Output :

```List-1: 1 2 7
List-2: 3 4 5 7
Intersection found at node with data: 7

List-3: 1 2 5
List-4: 3 4 5 7
No intersection found.

```

Click me to see the solution

## C Doubly Linked List [22 exercises with solution]

1. Write a program in C to create and display a doubly linked list.
Test Data :
Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8
Expected Output :

``` Data entered on the list are :
node 1 : 2
node 2 : 5
node 3 : 8
```

Click me to see the solution

2. Write a program in C to create a doubly linked list and display it in reverse order.
Test Data :
Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8
Expected Output :

``` Data in reverse order are :
Data in node 1 : 8
Data in node 2 : 5
Data in node 3 : 2
```

Click me to see the solution

3. Write a program in C to insert a node at the beginning of a doubly linked list.
Test Data and Expected Output :

``` Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8

Data entered in the list are :
node 1 : 2
node 2 : 5
node 3 : 8
Input data for the first node : 1

After insertion the new list are :
node 1 : 1
node 2 : 2
node 3 : 5
node 4 : 8
```

Click me to see the solution

4. Write a program in C to insert a new node at the end of a doubly linked list.
Test Data and Expected Output :

```Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8

Data entered in the list are :
node 1 : 2
node 2 : 5
node 3 : 8
Input data for the last node : 9

After insertion the new list are :
node 1 : 2
node 2 : 5
node 3 : 8
node 4 : 9
```

Click me to see the solution

5. Write a program in C to insert a new node at any position in a doubly linked list.
Test Data and Expected Output :

```Input the number of nodes (3 or more ): 3
Input data for node 1 : 2
Input data for node 2 : 4
Input data for node 3 : 5

Data entered in the list are :
node 1 : 2
node 2 : 4
node 3 : 5
Input the position ( 2 to 2 ) to insert a new node : 2
Input data for the position 2 : 3

After insertion the new list are :
node 1 : 2
node 2 : 3
node 3 : 4
node 4 : 5
```

Click me to see the solution

6. Write a program in C to insert a new node in the middle of a doubly linked list.
Test Data and Expected Output :

```  Doubly Linked List : Insert new node at the middle in a doubly linked list :
----------------------------------------------------------------------------------
Input the number of nodes (3 or more ): 3
Input data for node 1 : 2
Input data for node 2 : 4
Input data for node 3 : 5

Data entered in the list are :
node 1 : 2
node 2 : 4
node 3 : 5
Input the position ( 2 to 2 ) to insert a new node : 2
Input data for the position 2 : 3

After insertion the new list are :
node 1 : 2
node 2 : 3
node 3 : 4
node 4 : 5
```

Click me to see the solution

7. Write a program in C to delete a node from the beginning of a doubly linked list.
Test Data and Expected Output :

```Input the number of nodes (3 or more ): 3
Input data for node 1 : 1
Input data for node 2 : 2
Input data for node 3 : 3

Data entered in the list are :
node 1 : 1
node 2 : 2
node 3 : 3

After deletion the new list are :
node 1 : 2
node 2 : 3
```

Click me to see the solution

8. Write a program in C to delete a node from the last node of a doubly linked list.
Test Data and Expected Output :

```Input the number of nodes (3 or more ): 3
Input data for node 1 : 1
Input data for node 2 : 2
Input data for node 3 : 3

Data entered in the list are :
node 1 : 1
node 2 : 2
node 3 : 3

After deletion the new list are :
node 1 : 1
node 2 : 2
```

Click me to see the solution

9. Write a program in C to delete a node from any position in a doubly linked list.
Test Data and Expected Output :

``` Doubly Linked List : Delete node from any position of a doubly linked list :
----------------------------------------------------------------------------------
Input the number of nodes (3 or more ): 3
Input data for node 1 : 1
Input data for node 2 : 2
Input data for node 3 : 3

Data entered in the list are :
node 1 : 1
node 2 : 2
node 3 : 3
Input the position ( 1 to 3 ) to delete a node : 3

After deletion the new list are :
node 1 : 1
node 2 : 2
```

Click me to see the solution

10. Write a program in C to delete a node from the middle of a doubly linked list.
Test Data and Expected Output :

```Input the number of nodes (3 or more ): 3
Input data for node 1 : 1
Input data for node 2 : 2
Input data for node 3 : 3

Data entered in the list are :
node 1 : 1
node 2 : 2
node 3 : 3
Input the position ( 1 to 3 ) to delete a node : 2

After deletion the new list are :
node 1 : 1
node 2 : 3
```

Click me to see the solution

11. Write a program in C to find the maximum value in a doubly linked list.
Test Data :
Input the number of nodes : 3
Input data for node 1 : 5
Input data for node 2 : 9
Input data for node 3 : 1
Expected Output :

``` Data entered in the list are :
node 1 : 5
node 2 : 9
node 3 : 1

The Maximum Value in the Linked List : 9
```

Click me to see the solution

12. Write a program in C to create and display a circular linked list.
Test Data :
Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8
Expected Output :

``` Data entered in the list are :
Data 1 = 2
Data 2 = 5
Data 3 = 8
```

Click me to see the solution

13. Write a program in C to insert a node at the beginning of a circular linked list.
Test Data and Expected Output :

```Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8

Data entered in the list are :
Data 1 = 2
Data 2 = 5
Data 3 = 8
Input data to be inserted at the beginning : 1

After insertion the new list are :
Data 1 = 1
Data 2 = 2
Data 3 = 5
Data 4 = 8
```

Click me to see the solution

14. Write a program in C to insert a node at the end of a circular linked list.
Test Data and Expected Output :

```Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8

Data entered in the list are :
Data 1 = 2
Data 2 = 5
Data 3 = 8
Input the data to be inserted : 9

After insertion the new list are :
Data 1 = 2
Data 2 = 5
Data 3 = 8
Data 4 = 9
```

Click me to see the solution

15. Write a program in C to insert a node at any position in a circular linked list.
Test Data and Expected Output :

```Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8

Data entered in the list are :
Data 1 = 2
Data 2 = 5
Data 3 = 8
Input the position to insert a new node : 3
Input data for the position 3 : 7

After insertion the new list are :
Data 1 = 2
Data 2 = 5
Data 3 = 7
Data 4 = 8
```

Click me to see the solution

16. Write a program in C to delete a node from the beginning of a circular linked list.
Test Data :
Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8
Expected Output :

``` Data entered in the list are :
Data 1 = 2
Data 2 = 5
Data 3 = 8

The deleted node is -> 2
After deletion the new list are :
Data 1 = 5
Data 2 = 8
```

Click me to see the solution

17. Write a program in C to delete a node from the middle of a circular linked list.
Test Data and Expected Output :

```Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8

Data entered in the list are :
Data 1 = 2
Data 2 = 5
Data 3 = 8

Input the position to delete the node : 3

The deleted node is : 8
After deletion the new list are :
Data 1 = 2
Data 2 = 5
```

Click me to see the solution

18. Write a program in C to delete the node at the end of a circular linked list.
Test Data and Expected Output :

```Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 8

Data entered in the list are :
Data 1 = 2
Data 2 = 5
Data 3 = 8

The deleted node is : 8
After deletion the new list are :
Data 1 = 2
Data 2 = 5
```

Click me to see the solution

19. Write a program in C to search an element in a circular linked list.
Test Data and Expected Output :

``` Circular Linked List : Search an element in a circular linked list :
-------------------------------------------------------------------------
Input the number of nodes : 3
Input data for node 1 : 2
Input data for node 2 : 5
Input data for node 3 : 9

Data entered in the list are :
Data 1 = 2
Data 2 = 5
Data 3 = 9
Input the element you want to find : 5
Element found at node 2
```

Click me to see the solution

20. Write a C program to sort a given linked list by bubble sort.
Test Data and Expected Output : 5
15
33
49
6
65

``` Input number of elements in the linked list? Input the elements in the linked list:
Sorted order is:
6	15	33	49	65
```

Click me to see the solution

21. Write a C program to convert a Doubly Linked list into a string.
Test Data and Expected Output :

``` Input the number of nodes: 4
Input data for node 1 : 10
Input data for node 2 : 11
Input data for node 3 : 12
Input data for node 4 : 13

The doubly linked list in string format: 10 11 12 13

```

Click me to see the solution

22. Write a C program to convert a doubly linked list into an array and return it.
Test Data and Expected Output :

``` Input the number of nodes: 4
Input data for node 1 : 10
Input data for node 2 : 11
Input data for node 3 : 12
Input data for node 4 : 13

Doubly linked list in array format:
10 11 12 13
```

Click me to see the solution

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## C Programming: Tips of the Day

Why #define TRUE (1==1) in a C boolean macro instead of simply as 1?

This approach will use the actual boolean type (and resolve to true and false) if the compiler supports it. (specifically, C++)

However, it would be better to check whether C++ is in use (via the __cplusplus macro) and actually use true and false.

In a C compiler, this is equivalent to 0 and 1.

(note that removing the parentheses will break that due to order of operations)

Ref : https://bit.ly/3mbkkAr

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