BZOJ1493 : [NOI2007]项链工厂

设delta表示翻转后的增量，flip表示是否翻转，

第x个位置对应原来位置为(flip?n+2-x+delta:x-delta)%n

再根据x,y的大小关系以及flip的是否讨论出现在作用的区间

用线段树维护最左端最右端的颜色和块数

这种神级码农题我居然一遍AC…

#include<cstdio>
#define N 500010
int n,q,i,A[N],x,y,z,delta,flip,cx,cy,tot,l[N<<1],r[N<<1],cl[N<<1],cr[N<<1],sum[N<<1],tag[N<<1];char ch[10];
inline void read(int&a){char ch;while(!(((ch=getchar())>='0')&&(ch<='9')));a=ch-'0';while(((ch=getchar())>='0')&&(ch<='9'))(a*=10)+=ch-'0';}
inline void col1(int x,int p){cl[x]=cr[x]=tag[x]=p,sum[x]=1;}
inline void pb(int x){if(tag[x])col1(l[x],tag[x]),col1(r[x],tag[x]),tag[x]=0;}
inline void up(int x){cl[x]=cl[l[x]],cr[x]=cr[r[x]],sum[x]=sum[l[x]]+sum[r[x]]-(cr[l[x]]==cl[r[x]]);}
void build(int a,int b){
  int x=++tot;
  if(a==b){cl[x]=cr[x]=A[a],sum[x]=1;return;}
  int mid=(a+b)>>1;
  l[x]=tot+1,build(a,mid);
  r[x]=tot+1,build(mid+1,b);
  up(x);
}
void col(int x,int a,int b,int c,int d,int p){
  if(c<=a&&b<=d){col1(x,p);return;}
  pb(x);
  int mid=(a+b)>>1;
  if(c<=mid)col(l[x],a,mid,c,d,p);
  if(d>mid)col(r[x],mid+1,b,c,d,p);
  up(x);
}
int ask(int x,int a,int b,int c,int d){
  if(c<=a&&b<=d)return sum[x];
  pb(x);
  int mid=(a+b)>>1,t;
  if(d<=mid){t=ask(l[x],a,mid,c,d);return up(x),t;}
  if(c>mid){t=ask(r[x],mid+1,b,c,d);return up(x),t;}
  t=ask(l[x],a,mid,c,d)+ask(r[x],mid+1,b,c,d)-(cr[l[x]]==cl[r[x]]);
  return up(x),t;
}
int askcol(int x,int a,int b,int c){
  if(a==b)return cl[x];
  pb(x);
  int mid=(a+b)>>1,t=c<=mid?askcol(l[x],a,mid,c):askcol(r[x],mid+1,b,c);
  return up(x),t;
}
inline int form(int x){
  x=(flip?n+2-x+delta:x-delta)%n;
  while(x<=0)x+=n;
  return x;
}
int main(){
  for(read(n),read(i),i=1;i<=n;i++)read(A[i]);
  build(1,n);
  read(q);
  while(q--){
    scanf("%s",ch);
    if(ch[0]=='R')read(x),(delta+=x)%=n;
    else if(ch[0]=='F')flip^=1,delta*=-1;
    else if(ch[0]=='S')read(x),read(y),cx=askcol(1,1,n,x=form(x)),cy=askcol(1,1,n,y=form(y)),col(1,1,n,x,x,cy),col(1,1,n,y,y,cx);
    else if(ch[0]=='P'){
      read(x),read(y),read(z),x=form(x),y=form(y);
      if(!flip)x<=y?col(1,1,n,x,y,z):(col(1,1,n,x,n,z),col(1,1,n,1,y,z));else x>=y?col(1,1,n,y,x,z):(col(1,1,n,y,n,z),col(1,1,n,1,x,z));
    }else if(ch[0]=='C'&&ch[1]=='S'){
      read(x),read(y),x=form(x),y=form(y);
      if(!flip)printf("%d
",x<=y?ask(1,1,n,x,y):ask(1,1,n,x,n)+ask(1,1,n,1,y)-(cl[1]==cr[1]));else printf("%d
",x>=y?ask(1,1,n,y,x):ask(1,1,n,y,n)+ask(1,1,n,1,x)-(cl[1]==cr[1]));
    }else printf("%d
",sum[1]==1?1:sum[1]-(cl[1]==cr[1]));
  }
  return 0;
}