并查集-城市建设

package 搜索.并查集;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;


public class 城市建设 {
static class Edge {
public int to;
public int next;
public int price;


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


}


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


public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
n = sc.nextInt();
int m = sc.nextInt();
edge = new Edge[m + n];
pre = new int[n + 1];
for (int i = 0; i < m; i++) {
edge[i] = new Edge(sc.nextInt(), sc.nextInt(), sc.nextInt());
}
int count = 0;


for (int i = 1; i <= n; i++) {
int price = sc.nextInt();
if (price != -1) {
edge[m + count] = new Edge(0, i, price);
count++;
}
}
int result1 = dfs(n, m);
int result2 = dfs(n + 1, m + count);
if (result1 != -1) {
result2 = Math.min(result1, result2);
}
System.out.println(result2);


}


private static int dfs(int n, int m) {
init(m);
int maxPrice = 0;
int count = 0;
for (int i = 0; i < m; i++) {
if (union(edge[i].to, edge[i].next)) {
maxPrice += (edge[i].price);
count++;
} else if (edge[i].price < 0) {
maxPrice -= 1;
}
}
if (count != n - 1)
return -1;
return maxPrice;
}


private static void init(int m) {
for (int i = 0; i <= n; i++)
pre[i] = i;
Arrays.sort(edge, 0, m, new Comparator<Edge>() {
public int compare(Edge o1, Edge o2) {
return o1.price - o2.price;
}
});
}


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