Middle Element of Linked List in Kotlin

To find the middle element of a linked list, you can use the slow and fast pointer approach. Here are the steps:

1. Initialize two pointers, slow_ptr and fast_ptr, to the head of the linked list.
2. Move fast_ptr two nodes at a time and slow_ptr one node at a time until fast_ptr reaches the end of the linked list.
3. The node at which slow_ptr is pointing to is the middle element of the linked list.

class Node(var data: Int) {
    var next: Node? = null
}

Node class represents a node in the linked list, with an integer data and a next reference to the next node in the list.

fun findMiddleElement(head: Node?): Int? {
    var slowPtr = head
    var fastPtr = head

    while (fastPtr != null && fastPtr.next != null) {
        slowPtr = slowPtr?.next
        fastPtr = fastPtr.next?.next
    }

    return slowPtr?.data
}

The findMiddleElement function takes a head parameter, which is a reference to the head node of a linked list. The function returns the value of the middle element of the linked list, or null if the list is empty.

The function uses the slow and fast pointer approach to find the middle element. The slowPtr and fastPtr variables are initialized to the head node of the linked list.

The function then enters a loop, where the fastPtr variable moves ahead two nodes at a time, while the slowPtr variable moves ahead one node at a time. This continues until the fastPtr variable reaches the end of the list (i.e., its next reference is null), or the second-to-last node (i.e., its next reference is null but its next.next reference is not null).

At this point, the slowPtr variable is pointing to the middle element of the list, since it has moved halfway through the list while the fastPtr variable has moved all the way to the end (or close to the end). The function returns the value of the slowPtr node’s data field, which is the value of the middle element.

If the linked list is empty (i.e., the head parameter is null), then the function returns null, indicating that there is no middle element to be found.

class Node(var data: Int) {
    var next: Node? = null
}

fun findMiddleElement(head: Node?): Int? {
    var slowPtr = head
    var fastPtr = head

    while (fastPtr != null && fastPtr.next != null) {
        slowPtr = slowPtr?.next
        fastPtr = fastPtr.next?.next
    }

    return slowPtr?.data
}

fun main() {
    // create a linked list
    val head = Node(1)
    head.next = Node(2)
    head.next?.next = Node(3)
    head.next?.next?.next = Node(4)
    head.next?.next?.next?.next = Node(5)

    // find the middle element
    val middleElement = findMiddleElement(head)

    // print the middle element
    if (middleElement != null) {
        println("The middle element is $middleElement")
    } else {
        println("The linked list is empty")
    }
}

In the main function, a linked list is created and the findMiddleElement function is called to find the middle element. The value of the middle element is printed to the console.