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Middle of the Linked List - Linked List - Easy - LeetCode - MiniTV

Middle of the Linked List - Linked List - Easy - LeetCode - मिनी टीवी

Given a non-empty, singly linked list with head node head, return a middle node of linked list.

If there are two middle nodes, return the second middle node.

 

Example 1:

Input: [1,2,3,4,5]
Output: Node 3 from this list (Serialization: [3,4,5])
The returned node has value 3.  (The judge's serialization of this node is [3,4,5]).
Note that we returned a ListNode object ans, such that:
ans.val = 3, ans.next.val = 4, ans.next.next.val = 5, and ans.next.next.next = NULL.
Example 2:

Input: [1,2,3,4,5,6]
Output: Node 4 from this list (Serialization: [4,5,6])
Since the list has two middle nodes with values 3 and 4, we return the second one.
 

Note:

The number of nodes in the given list will be between 1 and 100.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int val=0, ListNode next=null) {
 *         this.val = val;
 *         this.next = next;
 *     }
 * }
 */
public class Solution {
    public ListNode MiddleNode(ListNode head) {
        ListNode slow = head;
        ListNode fast = head;
        if(head == null){
            return null;
        }
        
        if(head.next == null){
            return head;
        }
        
        if(head.next.next==null){
            return head.next;
        }
        
        while(fast != null && fast.next!=null){
            slow = slow.next;
            fast = fast.next.next;
        }
        
        return slow;
    }
}

Time Complexity: O(n)

Space Complexity: O(1)