[JZOJ4639]Angel Beats!

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 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int N=1e5+999;
 4 int fa[N][24];
 5 vector<int> v[N];
 6 int n;
 7 void ad(int x,int y){
 8     v[x].push_back(y);
 9     v[y].push_back(x);
10 }
11 int dep[N],siz[N],zson[N][24],ch[N];
12 void dfs(int fath,int x){
13     dep[x]=dep[fath]+1;
14     fa[x][0]=fath;
15     siz[x]=1;
16     zson[x][0]=-1;
17     int maxer=0;
18     for(int i=0;i<v[x].size();i++){
19     int dot=v[x][i];
20     if(dot!=fath){
21         dfs(x,dot);
22         ch[x]+=ch[dot]+siz[dot];
23         siz[x]+=siz[dot];
24         if(maxer<siz[dot]){maxer=siz[dot];zson[x][0]=dot;}
25     }
26     }
27 }
28 long long ssiz[N];
29 void dfs2(int fath,int x){
30     ssiz[x]=siz[x]+ssiz[fath];
31     for(int i=0;i<v[x].size();i++){
32     int dot=v[x][i];
33     if(dot!=fath){
34         dfs2(x,dot);
35     }
36     }
37 }
38 int lca(int x,int y){
39     if(x==y)return x;
40     if(dep[x]<dep[y])swap(x,y);
41     // X
42     for(int i=20;i>=0;i--)
43     if(dep[x]-(1<<i)>=dep[y])x=fa[x][i];
44     if(x==y)return x;
45     if(dep[y]==1)return y;
46     for(int i=20;i>=0;i--)
47     if(fa[x][i]!=fa[y][i]){x=fa[x][i];y=fa[y][i];}
48     return fa[x][0];
49 }
50 int q,root;
51 int as,qz[200];
52 int main(){
53 //    freopen("p.in","r",stdin);
54 //    freopen("p.out","w",stdout);
55     scanf("%d",&n);
56     for(int i=2;i<=n;i++){
57     int a,b;
58     scanf("%d",&b);
59     ad(i,b);
60         }
61     dfs(0,1);
62     dfs2(0,1);
63     for(int i=1;i<=20;i++)
64         for(int j=1;j<=n;j++)
65         fa[j][i]=fa[fa[j][i-1]][i-1];
66     for(int i=1;i<=20;i++)
67         for(int j=1;j<=n;j++)
68         zson[j][i]=zson[zson[j][i-1]][i-1];
69         cin>>q;
70         
71     for(int i=1;i<=q;i++){
72         long long ans=0;
73         int x,y,dist,all;
74         scanf("%d%d",&x,&y);
75         if(siz[x]<siz[y])swap(x,y);
76         ans=ch[x];
77         all=siz[x];
78         if(lca(x,y)!=x){
79             dist=dep[x]+dep[y]-2;
80             dist-=2*(dep[lca(x,y)]-1);
81             ans+=ch[y]+siz[y]*dist;
82             all+=siz[y];
83         }
84         int az=x;
85         for(int i=20;i>=0;i--){
86             int dot=zson[az][i];
87             if(siz[dot]*2>=all){
88             ans+=(all<<i)-2*(ssiz[dot]-ssiz[az]);
89             az=dot;
90             }
91         }
92         printf("%d\n",ans); 
93     }
94     return 0;
95 }
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posted @ 2019-05-18 17:01  周栎  阅读(143)  评论(0)  编辑  收藏  举报