BZOJ2002 [Hnoi2010]Bounce 弹飞绵羊

 1 /**************************************************************
 2     Problem: 2002
 3     User: rausen
 4     Language: C++
 5     Result: Accepted
 6     Time:1736 ms
 7     Memory:5700 kb
 8 ****************************************************************/
 9  
10 #include <cstdio>
11 #include <cmath>
12 #include <algorithm>
13  
14 using namespace std;
15  
16 int n, m, T, tot;
17 int w[250000], cnt[250000], to[250000], block[250000], a[250000];
18  
19 void build(){
20     int x = tot = 0, y;
21     while (x < n){
22         x += T, ++tot;
23         w[tot] = x;
24     }
25     w[tot] = min(n, w[tot]);
26      
27     for (int i = tot; i >= 1; --i)
28         for (int x = w[i]; x > w[i - 1]; --x){
29             y = x + a[x];
30             if (y <= w[i])
31                 to[x] = to[y], cnt[x] = cnt[y] + 1;
32             else to[x] = y, cnt[x] = 1;
33             block[x] = i;
34         }
35 }
36  
37 int query(int x){
38     int res = 0;
39     while (x <= n)
40         res += cnt[x], x = to[x];
41     return res;
42 }
43  
44 void change(int x){
45     int B = block[x], y;
46     for (int i = x; i > w[B - 1]; --i){
47         y = i + a[i];
48         if (y <= w[B])
49             to[i] = to[y], cnt[i] = cnt[y] + 1;
50         else to[i] = y, cnt[i] = 1;
51     }
52 }
53  
54 int main(){
55     scanf("%d", &n);
56     for (int i = 1; i <= n; ++i)
57         scanf("%d", a + i);
58     T = (int) sqrt(n);
59     build();
60  
61     scanf("%d", &m);
62     int X, Y, Z;
63     while (m--){
64         scanf("%d%d", &X, &Y);
65         if (X == 1)
66             printf("%d\n", query(Y + 1));
67         else {
68             scanf("%d", &Z);
69             a[Y + 1] = Z;
70             change(Y + 1);
71         }
72     }
73     return 0;
74 }