SBT

const int maxn=50010;const int INF=0x3f3f3f3f;struct SBT  {      int key,left,right,size;  } tree[maxn];    int root,top;    void left_rot(int &x)  {      int y = tree[x].right;      tree[x].right = tree[y].left;      tree[y].left = x;      tree[y].size = tree[x].size;//转上去的节点数量为先前此处节点的size      tree[x].size = tree[tree[x].left].size + tree[tree[x].right].size + 1;      x = y;  }    void right_rot(int &x)  {      int y = tree[x].left;      tree[x].left = tree[y].right;      tree[y].right = x;      tree[y].size = tree[x].size;      tree[x].size = tree[tree[x].left].size + tree[tree[x].right].size + 1;      x = y;  }    void maintain(int &x,bool flag)  {      if(flag == false)//左边      {          if(tree[tree[tree[x].left].left].size > tree[tree[x].right].size)//左孩子的左子树大于右孩子              right_rot(x);          else if(tree[tree[tree[x].left].right].size > tree[tree[x].right].size)//右孩子的右子树大于右孩子          {              left_rot(tree[x].left);              right_rot(x);          }          else return;      }      else //右边      {          if(tree[tree[tree[x].right].right].size > tree[tree[x].left].size)//右孩子的右子树大于左孩子              left_rot(x);          else if(tree[tree[tree[x].right].left].size > tree[tree[x].left].size)//右孩子的左子树大于左孩子          {              right_rot(tree[x].right);              left_rot(x);          }          else return;      }      maintain(tree[x].left,false);      maintain(tree[x].right,true);      maintain(x,true);      maintain(x,false);  }    /* *insert没有合并相同的元素，如果出现相同的元素则把它放到右子树上，这样能保证求第k小数的时候对相同元素也能正确 */  void insert(int &x,int key)  {      if(x == 0)      {          x = ++top;          tree[x].left = tree[x].right = 0;          tree[x].size = 1;          tree[x].key = key;      }      else      {          tree[x].size ++;          if(key < tree[x].key) insert(tree[x].left,key);          else  insert(tree[x].right,key);//相同元素插入到右子树中          maintain(x, key >= tree[x].key);//每次插入把平衡操作压入栈中      }  }    int del(int &p,int w)  {      if (tree[p].key==w || (tree[p].left==0 && w<tree[p].key) || (tree[p].right==0 && w>tree[p].key))      {          int delnum=tree[p].key;          if (tree[p].left==0 || tree[p].right==0) p=tree[p].left+tree[p].right;          else tree[p].key=del(tree[p].left,INF);          return delnum;      }      if (w<tree[p].key) return del(tree[p].left,w);      else return del(tree[p].right,w);  }    int  remove(int &x,int key)  {      int d_key;      //if(!x) return 0;      tree[x].size --;      if((key == tree[x].key)||(key < tree[x].key && tree[x].left == 0) ||              (key>tree[x].key && tree[x].right == 0))      {          d_key = tree[x].key;          if(tree[x].left && tree[x].right)          {              tree[x].key = remove(tree[x].left,tree[x].key+1);          }          else          {              x = tree[x].left + tree[x].right;          }      }      else if(key > tree[x].key)          d_key = remove(tree[x].right,key);      else if(key < tree[x].key)          d_key = remove(tree[x].left,key);      return d_key;  }    int getmin()  {      int x;      for(x = root ; tree[x].left; x = tree[x].left);      return tree[x].key;  }    int getmax()  {      int x;      for(x = root ; tree[x].right; x = tree[x].right);      return tree[x].key;  }    int select(int &x,int k)//求第k小数  {      int r = tree[tree[x].left].size + 1;      if(r == k) return tree[x].key;      else if(r < k) return select(tree[x].right,k - r);      else return select(tree[x].left,k);  }    int rank(int &x,int key)//求key排第几  {      if(key < tree[x].key)          return rank(tree[x].left,key);      else if(key > tree[x].key)          return rank(tree[x].right,key) + tree[tree[x].left].size + 1;      return tree[tree[x].left].size + 1;  }    int pred(int &x,int y,int key)//前驱 小于  {      if(x == 0) return y;      if(tree[x].key < key)          return pred(tree[x].right,x,key);      else return pred(tree[x].left,y,key);  }    int succ(int &x,int y,int key)//后继 大于  {      if(x == 0) return y;      if(tree[x].key > key)          return succ(tree[x].left,x,key);      else return succ(tree[x].right,y,key);  }