多了区间翻转，之后没了
区间翻转的标记记得在(kth)的时候下传
代码
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#define maxn 2100005
#define re register
int n,m,root,len,pos=1;
char val[maxn],S[maxn],opt[15];
int fa[maxn],sz[maxn],ch[maxn][2],rev[maxn];
inline void pushup(int x) {sz[x]=sz[ch[x][0]]+sz[ch[x][1]]+1;}
inline void pushdown(int x) {
if(!rev[x]) return;
std::swap(ch[ch[x][0]][0],ch[ch[x][0]][1]);
std::swap(ch[ch[x][1]][0],ch[ch[x][1]][1]);
rev[x]=0,rev[ch[x][0]]^=1,rev[ch[x][1]]^=1;
}
inline void rotate(int x) {
int y=fa[x],z=fa[y],k=ch[y][1]==x,w=ch[x][k^1];
ch[z][ch[z][1]==y]=x;ch[x][k^1]=y;ch[y][k]=w;
pushup(y),pushup(x),fa[w]=y,fa[y]=x,fa[x]=z;
}
inline void splay(int x,int goal) {
while(fa[x]!=goal) {
int y=fa[x];
if(fa[y]!=goal) rotate((ch[y][1]==x)^(ch[fa[y]][1]==y)?x:y);
rotate(x);
}
if(!goal) root=x;
}
inline int kth(int now) {
int x=root;
while(1) {
pushdown(x);
if(sz[ch[x][0]]+1==now) return x;
if(sz[ch[x][0]]>=now) x=ch[x][0];
else now-=sz[ch[x][0]]+1,x=ch[x][1];
}
}
int build(int x,int y,int f) {
if(x>y) return 0;
if(x==y) {
fa[++m]=f,sz[m]=1,val[m]=S[x];
return m;
}
int mid=x+y>>1,rt=++m;
fa[rt]=f,val[rt]=S[mid];
ch[rt][0]=build(x,mid-1,rt),ch[rt][1]=build(mid+1,y,rt);pushup(rt);
return rt;
}
int main()
{
scanf("%d",&n);
root=1,sz[1]=2,ch[1][1]=2,sz[2]=1,fa[2]=1;m=2;
while(n--) {
scanf("%s",opt);
if(opt[0]=='M') scanf("%d",&pos),pos++;
if(opt[0]=='P') pos--;
if(opt[0]=='N') pos++;
if(opt[0]=='I') {
scanf("%d",&len);S[0]=getchar();
for(re int i=1;i<=len;i++) S[i]=getchar();
int aa=kth(pos),bb=kth(pos+1);
splay(aa,0),splay(bb,aa);
int t=ch[root][1],rt=build(1,len,t);
ch[t][0]=rt;pushup(t);splay(t,0);
}
if(opt[0]=='D') {
scanf("%d",&len);
int aa=kth(pos),bb=kth(pos+len+1);
splay(aa,0),splay(bb,aa);
ch[ch[root][1]][0]=0;pushup(ch[root][1]);splay(ch[root][1],0);
}
if(opt[0]=='G') {
int aa=kth(pos),bb=kth(pos+2);
splay(aa,0),splay(bb,aa);
putchar(val[ch[ch[root][1]][0]]);
if(val[ch[ch[root][1]][0]]!=10) putchar(10);
}
if(opt[0]=='R') {
scanf("%d",&len);
int aa=kth(pos),bb=kth(pos+len+1);
splay(aa,0),splay(bb,aa);
int t=ch[ch[root][1]][0];
std::swap(ch[t][1],ch[t][0]),rev[t]^=1;
}
}
return 0;
}