Question

i wrote a simple program to sort numbers one by one for their repeat time and then inserts them one by one to tree. My problem is, i couldn’t insert root’s children because i couldn’t change the function below to call-by-reference type.

q parameter below needs to hold the root’s address value i think.

void insertNode(int data, node *q, node *parent){
    if(q == NULL){
        node *p = createNode(data);
        p -> parent = parent;
        p -> key = generateKey(p);
        int i;
        for(i = 0;table[i][1] != 0;i++);
        table[i][1] = p -> data;
        table[i][0] = p -> key;
        q = p;
    }
    else if(q -> left > q -> right || q -> left == q -> right){
        q -> right++;
        insertNode(data, q -> rightChild, q);
    }
    else if(q -> right > q -> left){
        q -> left++;
        insertNode(data, q -> leftChild, q);
    }
}

Answer 1

The node allocated in the “if(q == NULL){
}” block is lost; once the function returns, there is no pointer to it available to the caller. (the q=p; assignment does nothing)

UPDATE: the **p enables you to remove the recursion as well:

void insertNode(int data, node **qRef, node *parent){
  node *q;
  int i;

  for (   ; (q = *qRef) ; parent=q ) {
    if(q->left >= q->right) {
      q->right++;
      qRef = &q->rightChild;
    }
    else {
      q->left++;
      qRef = &q->leftChild;
    }
  }


  *qRef = q = createNode(data);
  q->parent = parent;
  q->key = generateKey(q);

  for(i=0; table[i][1] != 0; i++) {;}
  table[i][1] = q->data;
  table[i][0] = q->key;

}