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union_find_minCost.java
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union_find_minCost.java
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//http://koitp.org/problem/SDS_PRO_10_4/read/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Comparator;
class Edge {
int x, y, cost;
public Edge(int x, int y, int cost) {
this.x = x;
this.y = y;
this.cost = cost;
}
}
public class Main {
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int n = Integer.parseInt(br.readLine());
int m = Integer.parseInt(br.readLine());
int[] parent = new int[n+1];
int minCost = 0;
Edge[] e = new Edge[m];
for (int i = 1; i <= n; i++) {
parent[i] = i;
}
for (int i = 0; i < m; i++) {
String[] s = br.readLine().split(" ");
e[i] = new Edge(Integer.parseInt(s[0]), Integer.parseInt(s[1]), Integer.parseInt(s[2]));
}
Arrays.sort(e, new Comparator<Edge>() {
public int compare(Edge a, Edge b) {
return a.cost - b.cost;
}
});
for(int i=0; i<m; i++) {
int rootx = find(e[i].x, parent);
int rooty = find(e[i].y, parent);
if(rootx == rooty) {
continue;
} else {
parent[rootx] = rooty;
minCost = minCost + e[i].cost;
}
}
System.out.println(minCost);
}
private static int find(int x, int[] parent) {
if(x == parent[x]) {
return x;
} else {
parent[x] = find(parent[x], parent);
return parent[x];
}
}
}