題目連結
\(Splay\)先練到這吧（好像還有道毒瘤的維護數列誒，算了吧）
記錄下游標的編號，維護就是\(Splay\)基操了。
另外資料有坑，資料是\(Windows\)下生成了，回車是'\n\r'，我就被坑了。

#include <cstdio>
#include <algorithm>
using namespace std;
inline int read(){
    int s = 0, w = 1;
    char ch = getchar();
    while(ch < '0' || ch > '9'){if(ch == '-')w = -1;ch = getchar();}
    while(ch >= '0' && ch <= '9') s = s * 10 + ch - '0',ch = getchar();
    return s * w;
}
const int MAXINSERTLEN = 10000010;
struct SplayTree{
    char val;
    int ch[2], fa, size;
}t[MAXINSERTLEN];
char str[MAXINSERTLEN];
int num, root, n, len;
void pushup(int u){
    t[u].size = t[t[u].ch[0]].size + t[t[u].ch[1]].size + 1;
}
void rotate(int x){
    int y = t[x].fa; int z = t[y].fa; int k = t[y].ch[1] == x;
    t[z].ch[t[z].ch[1] == y] = x; t[x].fa = z;
    t[y].ch[k] = t[x].ch[k ^ 1]; t[t[x].ch[k ^ 1]].fa = y;
    t[x].ch[k ^ 1] = y; t[y].fa = x;
    pushup(y); pushup(x);
}
void Splay(int x, int goal){
    while(t[x].fa != goal){
      int y = t[x].fa; int z = t[y].fa;
      if(z != goal)
        (t[z].ch[0] == y) ^ (t[y].ch[0] == x) ? rotate(x) : rotate(y);
      rotate(x);
    }
    if(goal == 0) root = x;
}
int build(int l, int r){
    int id = ++num;
    int mid = (l + r) >> 1;
    t[id].val = str[mid];
    if(mid > l){
      t[id].ch[0] = build(l, mid - 1);
      t[t[id].ch[0]].fa = id;
    }
    if(mid < r){
      t[id].ch[1] = build(mid + 1, r);
      t[t[id].ch[1]].fa = id;
    }
    pushup(id);
    return id;
}
inline int findKth(int k){
    int u = root;
    while(1){
      if(t[t[u].ch[0]].size >= k) u = t[u].ch[0];
      else if(t[t[u].ch[0]].size == k - 1) return u;
      else k -= t[t[u].ch[0]].size + 1, u = t[u].ch[1];
    }
}
inline int next(int x, int mode){
    Splay(x, 0);
    int u = t[x].ch[mode]; mode ^= 1;
    while(t[u].ch[mode]) u = t[u].ch[mode];
    return u;
}
char opt;
int cur;
void print(int x){
    if(t[x].ch[0]) print(t[x].ch[0]);
    if(t[x].val != 1) printf("%c", t[x].val);
    if(t[x].ch[1]) print(t[x].ch[1]);
}
int main(){
    n = read();
    root = cur = ++num; t[num].val = 1;
    t[++num].fa = cur; t[num].val = 1;
    t[cur].ch[1] = num; t[num].size = 1; t[cur].size = 2;
    for(int i = 1; i <= n; ++i){
       opt = getchar();
       while(opt < 'A' || opt > 'Z') opt = getchar();
       if(opt == 'I'){
         len = read();
         for(int i = 1; i <= len; ++i){
            str[i] = getchar();
            while(str[i] < 32 || str[i] > 126) str[i] = getchar();
         }
         Splay(cur, 0);
         Splay(next(cur, 1), cur);
         t[t[root].ch[1]].ch[0] = (len = build(1, len));
         t[len].fa = t[root].ch[1];
         Splay(t[t[root].ch[1]].ch[0], 0);
       }
       else if(opt == 'G'){
         len = read();
         Splay(cur, 0);
         Splay(findKth(t[t[root].ch[0]].size + 2 + len), root);
         print(t[t[root].ch[1]].ch[0]);
         putchar('\n');
       }
       else if(opt == 'M')
         cur = findKth(read() + 1);
       else if(opt == 'P')
         cur = next(cur, 0);
       else if(opt == 'N')
         cur = next(cur, 1);
       else if(opt == 'D'){
         len = read();
         Splay(cur, 0);
         Splay(findKth(t[t[root].ch[0]].size + 2 + len), root);
         t[t[root].ch[1]].ch[0] = 0;
       }
    }
    return 0;
}