[20260313] BOJ / G4 / 행성 연결 / 이준희

Author: JHLEE325

JHLEE325/202603/13 BOJ G4 행성 연결.md

@@ -0,0 +1,74 @@
+```java
+import java.io.*;
+import java.util.*;
+
+class Edge implements Comparable<Edge> {
+    int u, v, weight;
+
+    public Edge(int u, int v, int weight) {
+        this.u = u;
+        this.v = v;
+        this.weight = weight;
+    }
+
+    @Override
+    public int compareTo(Edge o) {
+        return this.weight - o.weight;
+    }
+}
+
+public class Main {
+    
+    static int[] parent;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int N = Integer.parseInt(br.readLine());
+
+        List<Edge> edges = new ArrayList<>();
+        for (int i = 0; i < N; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            for (int j = 0; j < N; j++) {
+                int weight = Integer.parseInt(st.nextToken());
+                if (i < j) {
+                    edges.add(new Edge(i, j, weight));
+                }
+            }
+        }
+
+        Collections.sort(edges);
+
+        parent = new int[N];
+        for (int i = 0; i < N; i++) parent[i] = i;
+
+        long cost = 0;
+        int count = 0;
+
+        for (Edge edge : edges) {
+            if (union(edge.u, edge.v)) {
+                cost += edge.weight;
+                count++;
+                if (count == N - 1) break;
+            }
+        }
+
+        System.out.println(cost);
+    }
+
+    static int find(int x) {
+        if (parent[x] == x) return x;
+        return parent[x] = find(parent[x]);
+    }
+
+    static boolean union(int x, int y) {
+        x = find(x);
+        y = find(y);
+
+        if (x != y) {
+            parent[y] = x;
+            return true;
+        }
+        return false;
+    }
+}
+```