Finding middle element in a linked list

Finding Middle Node in Linked List

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Find the middle of a given linked list in C and Java

Hence we don't have direct access to the Linked List elements as we do in arrays. Make a local copy of that value at each level for later reference, and increment the ref count going into the next call. This programming question is mostly asked in a technical interviews. If so, the following function would have to be a member of that class. Infix expressions are the expressions that we normally use,eg. Dinesh is passionate about the latest Java technologies and loves to write technical blogs related to it.

How to Find Middle Element of Linked List in Java in One Pass in Java

You still access all the nodes once and half of them again. See the following C program. If there are even nodes, then there would be two middle nodes, we need to print second middle element. All that's different is when you iterate the extra half. Then traverse the list using first pointer element by element.

Finding Middle Node in Linked List

In that case initialing length with 0 make sense. He is currently working as a technology manager at a leading product and web development company. But frankly, there are no good answers, because it's a stupid interview question. Also In order to handle odd length e. It's hella easier to maintain that property than to waste time traversing the entire list every time I want the middle node.

algorithm

When the fast pointer reaches end slow pointer will reach the middle of the linked list. Also technique mentioned here to find middle node of LinkedList can be used to find 3rd element from Last or nth element from last in a LinkedList as well. You're making two separate passes through the list - it's just that you're doing them concurrently and not consecutively. Input: First line of input contains number of testcases T. Method 2: Find middle element of a linked list in single traversal.

algorithms

So the mid will move only half of the total length of the list. In this way when the fast pointer reaches the end the slow pointer will point to the middle element. I didn't thought that I can use two pointers or two variables to keep track of middle and last item, something I missed. In this tutorial, We are going to learn two approaches through which we can find middle element of a singly linked list. One of the most popular questions from data structures and algorithm mostly asked during the interview. Method 2 : Use 2 pointers say fast and slow starting from the head node increment the fast pointer by 2 and increment the slow pointer by 1. Hashing is done with help of a hash function that generates index for a given input, then this index can be used to search the elements, store an element, or remove that element from that index.

c++

The double pointer is a good idea, though it requires a decent amount more bookkeeping in your Linked List. Please suggest if it is efficient or can be improved? When we will not be able to move the fast pointer then at that particular time the position of slow pointer will give the middle node of the linked list. In this way, you will always have a copy of middle node and by the time you finish a single traverse you will have the middle node copied in mid1 if total count is odd , or copied in mid1 and mid2 if total count is even. To learn more, see our. If there are even nodes, then there would be two middle nodes, we need to print second middle element.

Find middle element of linked list in one scan

This works fine if there are odd number of elements in the list. How do you find middle element of LinkedList in one pass is a programming question often asked Java and non-Java programmers in telephonic Interview. The idea that answering this 'incorrectly' could have cost someone a job is slightly disconcerting. Now when you visit the first node i. If you demand an answer for a single pass, a student should respond that it isn't possible and that only 1. Yes we can find middle element of a singly linked list in single pass.

how to find middle element of a linked list

Now every time you get an odd count, you can move the mid1 one data forward to have the middle node and at just succeeding step when you find an even count, you can move the mid2 one data forward. It's stops when the pointer two ahead is null, and returns the current; it's clearly going to return the Node two away from the end. When it comes to the Spring Framework and Java, Dinesh tops the list! Unwinding, match the ref count to the local copy which is the node's number. By the way What is big O for best case and worst case for this solution? Unless I am missing something, this isn't one pass, it is 1. Anonymous, aspect here is coding, converting logic to code. If we know the size, we also know where the middle element is, so the solution is trivial.

Find the middle of a linked list

Since many programmers know that, in order to find length of linked list we need to first traverse through linked list till we find last node, which is pointing to null. I was asked to find middle item in a linked list in single pass and when I asked what is length of linked list they say, you need to find that as well. As if you think carefully you can solve this problem by using two pointers as mentioned in my last post on. Did you try implementing it that way? Step 3: When the fastPointer will reach the end of the linked list then slowPoint will be at the middle node, is it point we are looking for. This method although useful requires us to traverse the List 2 times. In our previous article, we have discussed how to.

Find middle element of linked list in one scan

Each Node contains data and address part. In this Java programming tutorial we will see a Java program which finds middle element of Linked List in one Iteration. If equal, return that node; else return the node returned from the recursive call. Ltd and was the first developer in his previous company, Paytm. Guido, Can you please elaborate? You hold the address of the first node as you do anyway , the address of the last node to optimize appends , and the number of nodes present. If there are even nodes, then there would be two middle nodes, we need to print second middle element.