二叉搜索树

struct node {
  int val;
  node *lch, *rch;
};
node *insert (node *p, int x) {
  if (p == NULL) {
    node *q = new node;
    q->val = x;
    q->lch = q->rch = NULL;
    return q;
  }
  else {
    if (x < p->val) {
      p->lch = insert(p->lch, x);
    }
    else {
      p->rch = insert(p->rch, x);
    }
    return p;
  }
}
bool find(node *p, int x) {
  if (p == NULL) {
    return false;
  }
  else {
    if (x == p->val) return true;
    else {
      if (x < p->val) {
        return find(p->lch, x);
      }
      else {
        return find(p->rch, x);
      }
    }
  }
}
node *remove(node *p, int x) {
  if (p == NULL) {
    return NULL;
  }
  else {
    if (x < p->val) {
      p->lch = remove(p->lch, x);
    }
    else {
      if (x > p->val) {
        p->rch = remove(p->rch, x);
      }
      else {
        if (p->lch == NULL) {
          node *q = p->rch;
          delete p;
          return q;
        }
        else {
          if (p->lch->rch == NULL) {
            node *q = p->lch;
            q->rch = p->rch;
            delete p;
            return q;
          }
          else {
            node *q;
            for (q = p->lch; q->rch->rch != NULL; q = q->rch);
            node *r = q->rch;
            q->rch = r->lch;
            r->lch = p->lch;
            r->rch = p->rch;
            delete p;
            return r;
          }
          return p;
        }
      }
    }
  }
}