kuangbin专题 专题九 连通图 HDU 4738 Caocao's Bridges

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <algorithm>
 4 using namespace std;
 5 
 6 const int N = (int)1e3+10;
 7 int n,m,tot,tim,solders;
 8 int head[N],low[N],dfn[N];
 9 struct node{
10     int to,nxt,w;
11 }e[(N*N)<<1];
12 
13 void init(){
14     for(int i = 0; i <= n; ++i){
15         head[i] = -1; dfn[i] = 0;
16     }
17     tot = tim = 0;
18     solders = (int)1e6;
19 }
20 
21 inline void add(int u,int v,int w){
22     e[tot].to = v; e[tot].w = w; e[tot].nxt = head[u]; head[u] = tot++;
23 }
24 
25 void tarjan(int now,int pre){
26     dfn[now] = low[now] = ++tim;
27     int to,pre_cnt = 0;
28     for(int o = head[now]; ~o; o = e[o].nxt){
29         to = e[o].to;
30         if(to == pre && pre_cnt == 0){ pre_cnt = 1; continue; }//重边处理
31         if(!dfn[to]){
32             tarjan(to,now);
33             low[now] = min(low[now],low[to]);
34             if(dfn[now] < low[to]) solders = min(solders,e[o].w);
35         }else low[now] = min(low[now],dfn[to]);
36     }
37 }
38 
39 int main(){
40 
41     int u,v,w;
42     while(~scanf("%d%d",&n,&m) && (n+m)){
43         init();
44         for(int i = 0;i < m; ++i){
45             scanf("%d%d%d",&u,&v,&w);
46             add(u,v,w); add(v,u,w);
47         }
48         tarjan(1,1);
49         for(int i = 1;i  <= n; ++i){
50             if(!dfn[i]){ solders = -2; break; }//岛本来就是分的
51         }
52         if(solders == -2) printf("0\n");
53         else{
54             if(solders == (int)1e6) solders = -1;//没法完成任务
55             printf("%d\n",!solders ? 1:solders);
56         }
57     }
58 
59     return 0;
60 }