BZOJ1787: [Ahoi2008]Meet 紧急集合

 1 #include<cstdio>
 2 #include<cstdlib>
 3 #include<cmath>
 4 #include<cstring>
 5 #include<algorithm>
 6 #include<iostream>
 7 #include<vector>
 8 #include<map>
 9 #include<set>
10 #include<queue>
11 #include<string>
12 #define inf 1000000000
13 #define maxn 500000+1000
14 #define maxm 500+100
15 #define eps 1e-10
16 #define ll long long
17 #define pa pair<int,int>
18 #define for0(i,n) for(int i=0;i<=(n);i++)
19 #define for1(i,n) for(int i=1;i<=(n);i++)
20 #define for2(i,x,y) for(int i=(x);i<=(y);i++)
21 using namespace std;
22 inline int read()
23 {
24     int x=0,f=1;char ch=getchar();
25     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
26     while(ch>=‘0‘&&ch<=‘9‘){x=10*x+ch-‘0‘;ch=getchar();}
27     return x*f;
28 }
29 int n,m,tot,ans,pos,head[maxn],dep[maxn],f[maxn][22];
30 struct edge{int next,go;}e[2*maxn];
31 void insert(int x,int y)
32 {
33     e[++tot].go=y;e[tot].next=head[x];head[x]=tot;
34 }
35 void dfs(int x)
36 {
37     for1(i,20)
38      if(dep[x]>=(1<<i))
39      f[x][i]=f[f[x][i-1]][i-1];
40      else break;
41     for(int i=head[x],y;i;i=e[i].next)
42      if(dep[y=e[i].go]==-1) 
43       {
44           dep[y]=dep[x]+1;
45           f[y][0]=x;
46           dfs(y);
47       }
48 }
49 int lca(int x,int y)
50 {
51     if(dep[x]<dep[y])swap(x,y);
52     int t=dep[x]-dep[y];
53     for0(i,20)
54      if(t&(1<<i))
55       x=f[x][i];
56     if(x==y)return x;
57     for(int i=20;i>=0;i--)
58      if(f[x][i]!=f[y][i])
59       x=f[x][i],y=f[y][i];
60     return f[x][0];    
61 }
62 void update(int x,int y,int z)
63 {
64     int t=lca(x,y),tt=lca(t,z),ttt=dep[x]+dep[y]+dep[z]-dep[t]-2*dep[tt];
65     if(ttt<ans)ans=ttt,pos=t;
66 }
67 int main()
68 {
69     freopen("input.txt","r",stdin);
70     freopen("output.txt","w",stdout);
71     n=read();m=read();
72     int x,y,z;
73     for1(i,n-1)x=read(),y=read(),insert(x,y),insert(y,x);
74     memset(dep,-1,sizeof(dep));
75     dep[1]=0;
76     dfs(1);
77     while(m--)
78      {
79          x=read();y=read();z=read();
80          ans=inf;pos=0;
81          update(x,y,z);
82          update(y,z,x);
83          update(z,x,y);
84          printf("%d %d\n",pos,ans);
85      }
86     return 0;
87 }