Thursday, April 8, 2010

Insert nodes into a linked list in a sorted fashion

The solution is to iterate down the list looking for the correct place to insert the new node. That could be the end of the list, or a point just before a node which is larger than the new node.

Note that we assume the memory for the new node has already been allocated and a pointer to that memory is being passed to this function.

// Special case code for the head end
void linkedListInsertSorted(struct node** headReference, struct node* newNode) 
  // Special case for the head end
  if (*headReference == NULL || (*headReference)->data >= newNode->data)
     newNode->next = *headReference;
     *headReference = newNode;
     // Locate the node before which the insertion is to happen!
     struct node* current = *headReference;
     while (current->next!=NULL && current->next->data < newNode->data)
        current = current->next;
     newNode->next = current->next;
     current->next = newNode;

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