LightOJ 1094

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<cctype>
#include<queue>
#include<vector>
#include<algorithm>

using namespace std;
typedef long long LL;
#define N 100100
#define INF 0x3f3f3f3f

int n, k, head[N], dist[N], Max, Index;
struct node
{
    int v, len, next;
} maps[N<<2];

void add(int u, int v, int len)
{
    maps[k].v=v;
    maps[k].len=len;
    maps[k].next=head[u];
    head[u]=k++;
}

void DFS(int u, int len)
{
    dist[u]=len;

    if(dist[u]>Max)
    {
        Max=dist[u];
        Index=u;
    }

    for(int i=head[u]; i!=-1; i=maps[i].next)
    {
        int v=maps[i].v;
        if(dist[v]==-1)
            DFS(v, dist[u]+maps[i].len);
    }
}

int main()
{
    int T, a, b, c, cas=1;
    scanf("%d", &T);

    while(T--)
    {
        k=1;
        memset(head, -1, sizeof(head));
        scanf("%d", &n);
        for(int i=0; i<n-1; i++)
        {
            scanf("%d%d%d", &a, &b, &c);
            add(a, b, c);
            add(b, a, c);
        }

        Max=Index=-1;
        memset(dist, -1, sizeof(dist));
        DFS(0, 0);

        memset(dist, -1, sizeof(dist));
        DFS(Index, 0);
        printf("Case %d: %d\n", cas++, Max);
    }
    return 0;
}