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题意：n个城市，m条双向路，要从k条中选择一个，使得到其他n-k个城市中的某个城市的距离最短。
思路：直接暴力 枚举。1A
代码实现
1/* ***********************************************
2Author :111qqz
3Created Time :2016年08月20日 星期六 21时02分14秒
4File Name :code/cf/#368/B.cpp
5************************************************ */
6#include <cstdio>
7#include <cstring>
8#include <iostream>
9#include <algorithm>
10#include <vector>
11#include <queue>
12#include <set>
13#include <deque>
14#include <map>
15#include <string>
16#include <cmath>
17#include <cstdlib>
18#include <ctime>
19#define fst first
20#define sec second
21#define lson l,m,rt<<1
22#define rson m+1,r,rt<<1|1
23#define ms(a,x) memset(a,x,sizeof(a))
24typedef long long LL;
25#define pi pair < int ,int >
26#define MP make_pair
27using namespace std;
28const double eps = 1E-8;
29const int dx4[4]={1,0,0,-1};
30const int dy4[4]={0,-1,1,0};
31const int inf = 0x3f3f3f3f;
32const int N =1E5+7;
33int n,m,k;
34vector <pair <int,LL> >edge[N];
35int b[N];
36bool cangku[N];
37int main()
38{
39 #ifndef ONLINE_JUDGE
40 freopen("code/in.txt","r",stdin);
41 #endif
42 ios::sync_with_stdio(false);
43 cin>>n>>m>>k;
44 ms(cangku,false);
45 for ( int i = 1 ; i <= m ; i++)
46 {
47 int u,v;
48 LL w;
49 cin>>u>>v>>w;
50 edge[u].push_back(make_pair(v,w));
51 edge[v].push_back(make_pair(u,w));
52 }
53 if (k==0)
54 {
55 cout<<-1<<endl;
56 return 0 ;
57 }
58 for ( int i = 1 ; i <= k ; i++)
59 {
60 cin>>b[i];
61 cangku[b[i]] = true;
62 }
63 if (k==n)
64 {
65 cout<<-1<<endl;
66 return 0;
67 }
68 LL ans = inf;
69 for (int i = 1 ; i <= k ; i++)
70 {
71 int u = b[i];
72 int siz = edge[u].size();
73 for (int j = 0 ; j < siz ; j++)
74 {
75 int v = edge[u][j].fst;
76 if (cangku[v]) continue;
77 LL w = edge[u][j].sec;
78 ans = min(ans,w);
79 }
80 }
81 if (ans==inf) ans = -1;
82 cout<<ans<<endl;
83 #ifndef ONLINE_JUDGE
84 fclose(stdin);
85 #endif
86 return 0;
87}