06-middle-of-list.md

Links

Leetcode

Expected Output

Intersection Node if Lists intersect else null

Approach

1. Slow and Fast Pointer a. Slow -> move 1 node per iteration b. Fast -> move 2 nodes per iteration

Logic

• With the above approach - we know that when fast pointer reaches the end/ ahead of end (null), the slow pointer will be pointing to the middle of the list

class Solution {
    public ListNode middleNode(ListNode head) {
        if(head == null || head.next == null) {
            return head;
        }

        ListNode slow = head;
        ListNode fast = head;

        while( fast != null && fast.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }

        return slow;
    }
}