The (Unofficial) ITWorx Technical Architecture Blog

Interviewing Question: Inserting into a Sorted Linked List

Posted by archworx on February 25, 2007

Due to the popularity of our Interviewing Question posts, we’ve decided to add yet another question. This time its easy and straight forward. You have a singly linked list of integers that are ordered ascendingly (for example -2,1,4,6,7). Can you devise an algorithm by which you insert a node into the linked list while maintaining its order. For example if you want to add a node containing the integer ‘5’ the linked list in the previous example will become (-2,1,4,5,6,7). Can you write the algorithm in C++ ?


14 Responses to “Interviewing Question: Inserting into a Sorted Linked List”

  1. yshahin said

    head is a pointer to the head of the list
    node is the link list element

    public void insertSort(node *item)
    node *curr=head, *prev=null;
    while(curr != null)
    if(curr->value >= item->value)
    prev = curr;
    curr = curr->next;
    if(prev == null)
    item->next = head;
    head = item;
    prev->next = item;
    item->next = curr;

  2. hellboy said

    heartily thanks…!

    wasted half-a-day for trying this by my own.
    then i discovered you.

    thanks again!

    more importantly, it worked..!!!

  3. hiren said

    I think there should be one more condition. what if (curr==null)?

    in that case:
    item->next = null;

    correct me if i am wrong.

    • Manish Singh said

      No it is not needed. what you are talking about is adding a node to an empty list. This condition will be handled by the if( prev == null ) case

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