一开始光知道pushdown却忘了pushup.........

#include
     
      #include
      
       #include
       
        #include
        
         #include
         
          #define MAXN 100010using namespace std;inline int read(){   int sum=0;   char ch=getchar();   while(ch<'0'||ch>'9')ch=getchar();   while(ch>='0'&&ch<='9')   {      sum=(sum<<1)+(sum<<3)+ch-'0';      ch=getchar();   }   return sum;}struct Treap{   struct Node   {       Node *ch[2];       int size,v,key;       bool rev;       void pushup()       {          size=ch[0]->size+ch[1]->size+1;       }   }null[MAXN],*root,*q[MAXN];   void swap(Node *&x,Node *&y)   {      Node *temp=x;      x=y;      y=temp;   }   void pushdown(Node *p)   {       if(!p->rev)return;       p->ch[0]->rev^=1;       p->ch[1]->rev^=1;       swap(p->ch[0],p->ch[1]);       p->rev=0;   }   int head,tail;   int sz;   Node *build(int l,int r)   {      if(l>r)return null;      int mid=(l+r)>>1;      null[mid].ch[0]=build(l,mid-1);      null[mid].ch[1]=build(mid+1,r);      null[mid].pushup();      return &null[mid];   }   void bfs()   {      q[1]=root;      head=tail=1;      while(head<=tail)      {         Node *x=q[head++];         x->v=++sz;         if(x->ch[1]!=null)q[++tail]=x->ch[1];         if(x->ch[0]!=null)q[++tail]=x->ch[0];      }   }   void Init(int n)   {       null->ch[0]=null->ch[1]=null;       for(int i=1;i<=n;i++)        null[i].ch[0]=null[i].ch[1]=null,null[i].size=1,null[i].key=i;       root=build(1,n);       bfs();   }   Node *Merge(Node *a,Node *b)   {      if(a==null)return b;      if(b==null)return a;      if(a->v
          
           v) { pushdown(a); a->ch[1]=Merge(a->ch[1],b); a->pushup(); return a; } else { pushdown(b); b->ch[0]=Merge(a,b->ch[0]); b->pushup(); return b; } } pair
           
             split(Node *p,int k) { if(p==null)return make_pair(null,null); pushdown(p); if(p->ch[0]->size>=k) { pair
            
              y=split(p->ch[0],k); p->ch[0]=y.second; p->pushup(); y.second=p; return y; } pair
             
               y=split(p->ch[1],k-p->ch[0]->size-1); p->ch[1]=y.first; p->pushup(); y.first=p; return y; } void Rev(int l,int r) { pair
              
                x=split(root,l-1); pair
               
                 y=split(x.second,r-l+1); y.first->rev^=1; root=Merge(Merge(x.first,y.first),y.second); } void Print(Node *p) { pushdown(p); if(p==null)return; Print(p->ch[0]); printf("%d ",p->key); Print(p->ch[1]); }}YY;int main(){ int n=read(),m=read(); YY.Init(n); while(m--) { int l=read(),r=read(); YY.Rev(l,r); } YY.Print(YY.root); return 0;}