Insertion to a cyclic sorted list given a pointer to a random node in the list.

icsl_2.cpp

node* icsl_2(node* head, node* n) {
    if(!head) {
        // list is empty, set head to the new node.
        return (head = n->next = n);
    }

    node* cur=head;
    node* prev;
    
    do {
        prev = cur;
        cur = cur->next;
        // normal situation
        if((prev->value <= n->value) && (n->value <= cur->value)) break;
        // new element is larger than the biggest or less than the smallest.
        if((prev->value > cur->value) && 
           (n->value < cur->value || n->value > prev->value)) 
           break;
    } while (cur != head);

    n->next = cur;
    prev->next = n;
    return head;
}