AVL平衡树的插入例程

/*
**AVL平衡树插入例程
**2014-5-30 11:44:50
*/

avlTree insert(elementType X, avlTree T){
  if(T == NULL){
    T = malloc(sizeof(struct avlTree));
    if(T == NULL) fatalError("Out of space!!!");
    T->element = X; T->height = 0;
    T->left = T->right = NULL;
  }else if(X < T->element){
    T->left = insert(X, T->left);
    if(height(T->left) - height(T->right) == 2){
      if(X < T->left->element) 
        T = singleRotateWithLeft(T);
      else T = doubleRotateWithLeft(T);
    }
  }else if(X > T->element){
    T->right = insert(X, T->right);
    if(height(T->right) - height(T->left) == 2){
      if(X > T->right->element)
        T = singleRotateWithRight(T);
      else T = doubleRotateWithRight(T);
    }
  }
  /*--假设X已经存在，那么啥都不用做--*/

  T->height = max(height(T->left), height(T->right)) + 1;
  return T;
}

static position singleRotateWithLeft(position k2){
  position k1 = k2-> left;  
  k2->left = k1->right;
  k1->right = k2;

  k2->height = max(height(k2->left), height(k2->right)) + 1;
  k1->height = max(height(k1->left), k2->height) + 1;
  return k1;
}

/*双右左旋就是先对T的右子树左单旋再对T本身右单旋*/
static position