[Week04] BOJ_4386: 별자리 만들기

weekly/week04/BOJ_4386_별자리만들기/sukangpunch.java

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+package study.week04;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.PriorityQueue;
+
+// 별자리 만들기
+public class BOJ_4386 {
+
+    static class Point{
+        int num;
+        double x;
+        double y;
+
+        public Point(int num, double x,double y){
+            this.num = num;
+            this.x = x;
+            this.y = y;
+        }
+    }
+
+    static class Edge{
+        int start;
+        int end;
+        double weight;
+
+        public Edge(int start, int end, double weight){
+            this.start = start;
+            this.end = end;
+            this.weight = weight;
+        }
+    }
+
+    static int[] parent;
+    static PriorityQueue<Edge> pq;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+
+        int N = Integer.parseInt(br.readLine());
+        Point [] points = new Point[N];
+
+        for(int i=0; i<N; i++){
+            String [] s = br.readLine().split(" ");
+            double x = Float.parseFloat(s[0]);
+            double y = Float.parseFloat(s[1]);
+
+            points[i] = new Point(i, x,y);
+        }
+
+        pq = new PriorityQueue<>((e1, e2) -> {
+            if(e1.weight < e2.weight) return -1;
+            return 1;
+        });
+
+        for (int i=0; i<N; i++){
+            for (int j = i+1; j<N; j++){
+                double weight = distance(points[i], points[j]);
+                pq.add(new Edge(points[i].num, points[j].num, weight));
+            }
+        }
+
+        parent = new int[N];
+        for(int i=0; i<N; i++){
+            parent[i] = i;
+        }
+
+        double ans = 0;
+
+        while(!pq.isEmpty()){
+            Edge edge = pq.poll();
+            int start = edge.start;
+            int end = edge.end;
+            double cost = edge.weight;
+
+            if(find(start) != find(end)){
+                ans += cost;
+                union(start, end);
+            }
+        }
+
+        System.out.println(ans);
+
+    }
+
+    public static void union(int x, int y){
+        int rootA = find(x);
+        int rootB = find(y);
+        parent[Math.min(rootA, rootB)] = Math.max(rootA, rootB);
+    }
+
+    private static int find(int x) {
+        if(x != parent[x]){
+            parent[x] = find(parent[x]);
+        }
+
+        return parent[x];
+    }
+
+    private static double distance(Point p1, Point p2) {
+        return Math.sqrt(Math.pow(p1.x - p2.x, 2) + Math.pow(p1.y - p2.y, 2));
+    }
+}