题意：在字符串中插入字符，问第i个字符是谁

题解：块状链表，不知为什么splay超时= =！

View Code 
 1 #include<cstdio>
 2 #include<cstring>
 3 #include<cmath>
 4 #include<algorithm>
 5 using namespace std;
 6 const int maxn=1005000;
 7 int bs,top;
 8 struct Block
 9 {
10     int size,next;
11     char s[3000];
12     void push_back(char ch)
13     {
14         s[size++]=ch;
15     }
16     void insert(int pos,char ch)
17     {
18         for(int i=size++;i>pos;i--)
19             s[i]=s[i-1];
20         s[pos]=ch;
21     }
22 }block[3000];
23 void update(int x)
24 {
25     if(block[x].size<bs*2)
26         return;
27     ++top;
28     int i,j,k=block[x].size;
29     for(i=bs,j=0;i<k;i++,j++)
30         block[top].s[j]=block[x].s[i];
31     block[top].size=j;
32     block[x].size=bs;
33     block[top].next=block[x].next;
34     block[x].next=top;
35 }
36 int main()
37 {
38     char s[maxn];
39     gets(s);
40     int len=strlen(s),m;
41     scanf("%d",&m);
42     bs=sqrt((double)(len+m))+1;
43     top=0;
44     block[0].size=0;
45     for(int i=0;i<len;i++)
46     {
47         if(block[top].size==bs)
48         {
49             block[top].next=top+1;
50             block[++top].size=0;
51         }
52         block[top].push_back(s[i]);
53     }
54     block[top].next=-1;
55     while(m--)
56     {
57         char op,ch;
58         int pos,k;
59         scanf(" %c",&op);
60         if(op=='Q')
61         {
62             scanf("%d",&pos);
63             k=0;
64             while(pos>block[k].size)
65                 pos-=block[k].size,k=block[k].next;
66             printf("%c\n",block[k].s[pos-1]);
67         }
68         else
69         {
70             scanf(" %c %d",&ch,&pos);
71             k=0;
72             while(block[k].next!=-1&&pos>block[k].size)
73                 pos-=block[k].size,k=block[k].next;
74             block[k].insert(min(pos-1,block[k].size+1),ch);
75             update(k);
76         }
77     }
78     return 0;
79 }