Inserting into Sorted LinkedList Java

Question

I have this code below where I am inserting a new integer into a sorted LinkedList of ints but I do not think it is the \"correct\" way of doing things as I know there are s

Answer 1

@Atrakeur

"sorting all the list each time you add a new element isn't efficient"

That's true, but if you need the list to always be in a sorted state, it is really the only option.

"The best way is to insert the element directly where it has to be (at his correct position). For this, you can loop all the positions to find where this number belong to"

This is exactly what the example code does.

"or use Collections.binarySearch to let this highly optimised search algorithm do this job for you"

Binary search is efficient, but only for random-access lists. So you could use an array list instead of a linked list, but then you have to deal with memory copies as the list grows. You're also going to consume more memory than you need if the capacity of the list is higher than the actual number of elements (which is pretty common).

So which data structure/approach to take is going to depend a lot on your storage and access requirements.

[edit] Actually, there is one problem with the sample code: it results in multiple scans of the list when looping.

int i = 0;
while (llist.get(i) < val) {
    i++;
}
llist.add(i, val);

The call to get(i) is going to traverse the list once to get to the ith position. Then the call to add(i, val) traverses it again. So this will be very slow.

A better approach would be to use a ListIterator to traverse the list and perform insertion. This interface defines an add() method that can be used to insert the element at the current position.