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Insert in Middle of Linked List

Tags : linkedlist, geeksforgeeks, cpp, easy

Problem Statement - link #

Given a linked list of size N and a key. The task is to insert the key in the middle of the linked list.

Your Task: The task is to complete the function insertInMiddle() which takes head reference and element to be inserted as the arguments. The printing is done automatically by the driver code.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Examples #

Example 1:

Input:
LinkedList = 1->2->4
key = 3
Output: 1 2 3 4
Explanation: The new element is inserted
after the current middle element in the
linked list.

Example 2:

Input:
LinkedList = 10->20->40->50
key = 30
Output: 10 20 30 40 50
Explanation: The new element is inserted
after the current middle element in the
linked list and Hence, the output is
10 20 30 40 50.

Constraints #

Solutions #

class Solution{
    public:
    /*
    struct Node {
    int data;
    struct Node *next;
    Node(int x) {
        data = x;
        next = NULL;
    }
    };
    */

    //Function to insert a node in the middle of the linked list.
    Node* insertInMiddle(Node* head, int x)
    {
        // Code here
        Node* fast = head;
        Node* slow = head;
        while(fast->next!=NULL && fast->next->next!=NULL){
            fast=fast->next->next;
            slow=slow->next;
        }
        Node* temp = new Node(x);
        temp->next = slow->next;
        slow->next = temp;
        return head;
    }
};