hdu 4118 dfs

  1 #pragma comment(linker, "/STACK:10240000000000,10240000000000")
  2 #include<stdio.h>
  3 #include<algorithm>
  4 #include<iostream>
  5 #include<string.h>
  6 using namespace std;
  7 const int MAXN=200010;
  8 struct Node
  9 {
 10     int to,next;
 11     int len;
 12 }edge[MAXN*2];
 13 
 14 int head[MAXN];
 15 int tol;
 16 int num[MAXN];//从这个点以下的结点数
 17 long long ans;
 18 void init()
 19 {
 20     tol=0;
 21     memset(head,-1,sizeof(head));
 22     memset(num,0,sizeof(num));
 23 }
 24 void add(int a,int b,int len)
 25 {
 26     edge[tol].to=b;
 27     edge[tol].len=len;
 28     edge[tol].next=head[a];
 29     head[a]=tol++;
 30 
 31     edge[tol].to=a;
 32     edge[tol].len=len;
 33     edge[tol].next=head[b];
 34     head[b]=tol++;
 35 }
 36 int n;
 37 //递归形式会超出内存
 38 void dfs(int u,int pre)
 39 {
 40     for(int i=head[u];i!=-1;i=edge[i].next)
 41     {
 42         int v=edge[i].to;
 43         if(v==pre)continue;
 44         dfs(v,u);
 45         num[u]+=num[v];
 46         ans+=(long long)edge[i].len*min(num[v],n-num[v]);
 47     }
 48     num[u]++;
 49 }
 50 
 51 /*int sta[MAXN];
 52 bool vis[MAXN];
 53 void dfs(int u)
 54 {
 55     memset(vis,false,sizeof(vis));
 56     int top=0;
 57     sta[top++]=u;
 58     vis[u]=true;
 59     while(top>0)
 60     {
 61         bool flag=true;
 62         int t=sta[top-1];
 63         for(int i=head[t];i!=-1;i=edge[i].next)
 64         {
 65             int v=edge[i].to;
 66             if(vis[v])continue;
 67             flag=false;
 68             sta[top++]=v;
 69             vis[v]=true;
 70         }
 71         if(!flag)continue;
 72         top--;
 73         for(int i=head[t];i!=-1;i=edge[i].next)
 74         {
 75             int v=edge[i].to;
 76             if(num[v]!=0)
 77             {
 78                 num[t]+=num[v];
 79                 ans+=(long long)edge[i].len*min(num[v],n-num[v]);
 80             }
 81         }
 82         num[t]++;
 83     }
 84 }*/
 85 
 86 int main()
 87 {
 88     int T;
 89     int iCase=0;
 90     int u,v,w;
 91     #ifndef ONLINE_JUDGE
 92     freopen("1.in","r",stdin);
 93     #endif
 94     scanf("%d",&T);
 95     while(T--)
 96     {
 97         iCase++;
 98         scanf("%d",&n);
 99         init();
100         ans=0;
101         for(int i=1;i<n;i++)
102         {
103             scanf("%d%d%d",&u,&v,&w);
104             add(u,v,w);
105         }
106         dfs(1,0);
107         printf("Case #%d: %I64d\n",iCase,ans*2);
108     }
109     return 0;
110 }