并查集-国王的烦恼

package 搜索.并查集;


import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;


public class 国王的烦恼 {
static class Edge {
public int to;
public int next;
public int day;


public Edge(int to, int next, int day) {
super();
this.to = to;
this.next = next;
this.day = day;
}


}


static Edge[] edge;
static int pre[];


public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int m = sc.nextInt();
edge = new Edge[m];
pre = new int[n + 1];
for (int i = 0; i <= n; i++)
pre[i] = i;
for (int i = 0; i < m; i++) {
edge[i] = new Edge(sc.nextInt(), sc.nextInt(), sc.nextInt());
}
Arrays.sort(edge, new Comparator<Edge>() {
public int compare(Edge o1, Edge o2) {
return o2.day - o1.day;
}
});
int lastDay = -1;
int count = 0;
int visited = 0;
for (int i = 0; i < m; i++) {
if (union(edge[i].to, edge[i].next)) {
if (lastDay != edge[i].day) {
lastDay = edge[i].day;
count++;
}
visited++;
}
if (visited == n - 1)
break;
}
System.out.println(count);
}


private static boolean union(int to, int next) {
int x = find(to);
int y = find(next);
if (x != y) {
pre[x] = y;
return true;
}
return false;
}


private static int find(int to) {
int root = to;
while (root != pre[root]) {
root = pre[root];
}
int temp;
while (to != root) {
temp = pre[to];
pre[to] = root;
to = temp;
}
return root;
}


}