poj2395 Out of Hay

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <map>
 5 #include <queue>
 6 using namespace std;
 7 typedef __int64 LL;
 8 const int maxn = 2e3 + 10;
 9 const int maxm = 1e4 + 10;
10 const int inf = 1e9 + 1e8;
11 struct Edge{
12     int from, to, next, c;
13     bool operator < (const Edge& rhs) const{
14         return c < rhs.c;
15     }
16 }edge[maxm << 1];
17 struct Point{
18     int x, y, c;
19     bool operator < (const Point& rhs) const{
20         return x < rhs.x || (x == rhs.x && y < rhs.y) || (x == rhs.x && y == rhs.y && c < rhs.c);
21     }
22 };
23 int head[maxn], N;
24 Point a[maxm];
25 int n, m, k;
26 int ans;
27 bool vis[maxn];
28 
29 void addEdge(int u, int v, int c){
30     edge[N].next = head[u];
31     edge[N].from = u;
32     edge[N].to = v;
33     edge[N].c = c;
34     head[u] = N++;
35 }
36 
37 int fa[maxn];
38 
39 int find(int u){
40     if(fa[u] == -1 || fa[u] == u) return u;
41     return fa[u] = find(fa[u]);
42 }
43 int main(){
44     //freopen("in.txt", "r", stdin);
45     while(~scanf("%d%d", &n, &m)){
46         N = 0;
47         memset(head, -1, sizeof head);
48         for(int i = 0; i < m; i++){
49             scanf("%d%d%d", &a[i].x, &a[i].y, &a[i].c);
50             if(a[i].x > a[i].y) swap(a[i].x, a[i].y);
51         }
52         sort(a, a + m);
53         k = 0;
54         for(int i = 0; i < m; i++){
55             a[k++] = a[i];
56             while(i < m - 1 && a[i].x == a[i + 1].x && a[i].y == a[i + 1].y) ++i;
57         }
58         for(int i = 0; i < k; i++) addEdge(a[i].x, a[i].y, a[i].c);
59         sort(edge, edge + N);
60         int ans = -1;
61         memset(fa, -1, sizeof fa);
62         for(int i = 0; i < N; i++){
63             int u = edge[i].from, v = edge[i].to;
64             int fu = find(u), fv = find(v);
65             if(fu != fv) fa[fv] = fu, ans = max(ans, edge[i].c);
66         }
67         printf("%d\n", ans);
68     }
69     return 0;
70 }