[20250911] BOJ / G3 / 별자리 만들기 / 이준희

Author: JHLEE325

JHLEE325/202509/11 BOJ G3 별자리 만들기.md

@@ -0,0 +1,87 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    static class node {
+        double x, y;
+
+        public node(double x, double y) {
+            this.x = x;
+            this.y = y;
+        }
+    }
+
+    static class edge implements Comparable<edge> {
+        int from, to;
+        double weight;
+
+        public edge(int from, int to, double weight) {
+            this.from = from;
+            this.to = to;
+            this.weight = weight;
+        }
+
+        @Override
+        public int compareTo(edge o) {
+            return Double.compare(this.weight, o.weight);
+        }
+    }
+
+    static int[] parent;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st;
+
+        int n = Integer.parseInt(br.readLine());
+        node[] stars = new node[n];
+
+        for (int i = 0; i < n; i++) {
+            st = new StringTokenizer(br.readLine());
+            double x = Double.parseDouble(st.nextToken());
+            double y = Double.parseDouble(st.nextToken());
+            stars[i] = new node(x, y);
+        }
+
+        List<edge> edges = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                double dist = Math.sqrt(Math.pow(stars[i].x - stars[j].x, 2) + Math.pow(stars[i].y - stars[j].y, 2));
+                edges.add(new edge(i, j, dist));
+            }
+        }
+
+        Collections.sort(edges);
+
+        parent = new int[n];
+        for (int i = 0; i < n; i++) parent[i] = i;
+
+        double result = 0;
+        int cnt = 0;
+        for (edge e : edges) {
+            if (union(e.from, e.to)) {
+                result += e.weight;
+                cnt++;
+                if (cnt == n - 1) break;
+            }
+        }
+
+        System.out.printf("%.2f\n", result);
+    }
+
+    static int find(int x) {
+        if (parent[x] == x) return x;
+        return parent[x] = find(parent[x]);
+    }
+
+    static boolean union(int a, int b) {
+        a = find(a);
+        b = find(b);
+        if (a == b) return false;
+        parent[b] = a;
+        return true;
+    }
+}
+```