修复公路

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 #include <algorithm>
 5 #define maxn 10000005
 6 using namespace std;
 7 struct Edge{
 8     int from,to,dis;
 9     bool operator<(const Edge &rhs)const{
10         return dis < rhs.dis;
11     }
12 };
13 Edge edge[maxn];
14 int n,m,ans;
15 inline int read(){
16     int num = 0;
17     char c;
18     while ((c = getchar()) == ‘ ‘ || c == ‘\n‘ || c == ‘\r‘);
19     num = c - ‘0‘;
20     while (isdigit(c = getchar()))
21         num = num * 10 + c - ‘0‘;
22     return num;
23 }
24 int father[maxn];
25 void init(){
26     for (int i=1;i<=n;i++)
27         father[i] = i;
28 }
29 int find(int x){
30     if (father[x] == x)
31         return father[x];
32     return father[x] = find(father[x]);
33 }
34 void merge(int x,int y){
35     father[find(x)] = find(y);
36 }
37 
38 
39 int main(){
40     n = read();m = read();
41     for (register int i=1;i<=m;i++){
42         edge[i].from = read();
43         edge[i].to = read();
44         edge[i].dis = read();
45     }
46     int totedge = 0;
47     sort(edge+1,edge+m+1);
48     init();
49     for (register int i=1;i<=m;i++){
50         if (find(edge[i].from)!=find(edge[i].to)){
51             ans=max(ans,edge[i].dis);
52             merge(edge[i].from,edge[i].to);
53             totedge++;
54         }
55     }
56     if (totedge < n-1)
57         printf("-1");
58     else
59         printf("%d",ans);
60     return 0;
61 }