﻿ C++ - Find middle element in a single linked list

# C++ Linked List Exercises: Find middle element in a single linked list

## C++ Linked List: Exercise-6 with Solution

Write a C++ program to find the middle element of a given Linked List.

Test Data:
Original list:
9 7 5 3 1
Middle element of the said list:
5
Original list:
7 5 3 1
Middle element of the said list:
3
Explanation: The second node of the list is returned since it has the values 5 and 3.

Sample Solution:

C++ Code:

``````#include <iostream> // Including input-output stream header file

using namespace std; // Using standard namespace

// Structure for defining a Node
struct Node {
int num; // Data field to store a number
Node *next; // Pointer to the next node
}; // Node constructed

int sz = 0; // Initializing variable to keep track of the size of the linked list

// Function to insert a node at the beginning of the linked list
void insert(Node** head, int num) {
Node* new_Node = new Node(); // Creating a new node
new_Node->num = num; // Assigning data to the new node
new_Node->next = *head; // Pointing the new node to the current head
sz++; // Increasing the size of the linked list
}

// Function to find the middle element of a linked list
if (!head) return -1; // If the list is empty, return -1 (no middle element)
int c = 0; // Counter variable to keep track of the position in the list
Node *middle = head; // Pointer for the middle element initially set to head
if (c % 2 != 0) middle = middle->next; // Update the middle pointer for odd positions
c++; // Incrementing the counter
}
return middle->num; // Return the value of the middle element
}

// Display all nodes in the linked list
void display_all_nodes(Node* node) {
while (node != NULL) {
cout << node->num << " "; // Displaying the data in the current node
node = node->next; // Move to the next node
}
}

int main() {

insert(&head, 1); // Inserting a node with value 1
insert(&head, 3); // Inserting a node with value 3
insert(&head, 5); // Inserting a node with value 5
insert(&head, 7); // Inserting a node with value 7

cout << "Original list:\n"; // Displaying message for the original list
display_all_nodes(head); // Displaying all nodes in the original list

cout << "\nMiddle element of the said list:"; // Displaying message for the middle element
cout << "\n" << get_Middle(head) << "\n"; // Finding and displaying the middle element

cout << "\nOriginal list:\n"; // Displaying message for the updated list after insertion
insert(&head, 9); // Inserting a node with value 9
display_all_nodes(head); // Displaying all nodes in the updated list

cout << "\nMiddle element of the said list:"; // Displaying message for the middle element
cout << "\n" << get_Middle(head); // Finding and displaying the middle element in the updated list

cout << endl; // Displaying newline
return 0; // Returning from the main function
}
``````

Sample Output:

```Original list:
7 5 3 1
Middle element of the said list:
3

Original list:
9 7 5 3 1
Middle element of the said list:
5
```

Flowchart:

CPP Code Editor: