BZOJ1103[POI2007]大都市meg 题解

 1 #include<cstdio>
 2 #include<iostream>
 3 #define M 300000 
 4 using namespace std;
 5 
 6 int n,m,cnt,dfn,to[M],next[M],head[M],c[M],come[M],leave[M];
 7 
 8 int read()
 9 {
10     int x=0,y=1;
11     char ch=getchar();
12     while (ch<‘0‘ || ch>‘9‘) {if (ch==‘-‘) y=-1;ch=getchar();}
13     while (ch>=‘0‘ && ch<=‘9‘) {x=x*10+ch-48;ch=getchar();}
14     return x*y;
15 }
16 
17 void ins(int x,int y)
18 {
19      to[++cnt]=y,next[cnt]=head[x],head[x]=cnt;
20 }
21 
22 void dfs(int x)
23 {
24      come[x]=++dfn;
25      for (int i=head[x];i;i=next[i]) dfs(to[i]);
26      leave[x]=dfn;
27 }
28 
29 void add(int x,int y)
30 {
31      for (;x<=n;x+=x&-x) c[x]+=y;
32 }
33 
34 int sum(int x)
35 {
36     int ans=0;
37     for (;x;x-=x&-x) ans+=c[x];
38     return ans;
39 }
40 
41 int main()
42 {
43     int i,j,x,y;
44     n=read();
45     for (i=1;i<n;i++) x=read(),y=read(),ins(x,y);
46     dfs(1);
47     m=read();
48     for (i=2;i<=n;i++) add(come[i],1),add(leave[i]+1,-1);
49     for (i=1;i<n+m;i++)
50     {
51         char ch=getchar();
52         while (ch<‘A‘ || ch>‘Z‘) ch=getchar();
53         if (ch==‘W‘) printf("%d\n",sum(come[read()]));
54         else x=read(),y=read(),add(come[y],-1),add(leave[y]+1,1);
55     }scanf("%d",&n);
56     return 0;
57 }