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Java

Posted by Jason Ladieu
Jason Ladieu
10,635 Points

Linked list recursion processing

Recursion is going to be the death of me... All kidding aside, is there a kind soul out there who can help me understand how this recursive method is processing a linked list of integers? I do not understand the logic, and I think is it mainly the recursion that is throwing me off. I fear I need some detailed insight into the logic happening here.

public class IntNode {
  int item; // One of the integers in the list. 
  IntNode next; // Pointer to the next node in the list.
}

/**
* Compute the sum of all the integers in a linked list of integers. 
* @param head a pointer to the first node in the linked list
*/
public static int addItemsInList( IntNode head ) { 
    if ( head == null ) {
        // Base case: The list is empty, so the sum is zero. 
    return 0;
} else {
      // Recursive case: The list is non-empty. Find the sum of
      // the tail list, and add that to the item in the head node.
      // (Note that this case could be written simply as
      // return head.item + addItemsInList( head.next );)
    int listsum = head.item;
    int tailsum = addItemsInList( head.next ); 
    listsum = listsum + tailsum;
    return listsum;
    }
}