Merge pull request #256 from Coding-Crew-Forever/hh830/algorithm

[2025년 8월 셋째주 / hh830] 그래프 이론

Author: github-actions[bot]

hh830/BOJ_9372.java

@@ -0,0 +1,56 @@
+import java.io.*;
+import java.util.*;
+
+public class BOJ_9372 {
+    private static List<List<Integer>> graph;
+    private static boolean[] visited;
+    private static int count;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
+        StringBuilder stringBuilder = new StringBuilder();
+
+        int T = Integer.parseInt(bufferedReader.readLine());
+
+        while (T > 0) {
+            StringTokenizer stringTokenizer = new StringTokenizer(bufferedReader.readLine());
+            int N = Integer.parseInt(stringTokenizer.nextToken());
+            int M = Integer.parseInt(stringTokenizer.nextToken());
+
+            graph = new ArrayList<>();
+
+            for (int i = 0; i <= N; i++) {
+                graph.add(new ArrayList<>());
+            }
+            visited = new boolean[N + 1];
+            count = 0;
+
+            for (int i = 0; i < M; i++) {
+                stringTokenizer = new StringTokenizer(bufferedReader.readLine());
+                int a = Integer.parseInt(stringTokenizer.nextToken());
+                int b = Integer.parseInt(stringTokenizer.nextToken());
+
+                graph.get(a).add(b);
+                graph.get(b).add(a);
+            }
+
+            dfs(1);
+
+            stringBuilder.append(count).append("\n");
+
+            T--;
+        }
+
+        System.out.print(stringBuilder);
+    }
+
+    private static void dfs(int node) {
+        visited[node] = true;
+        for (int next : graph.get(node)) {
+            if (!visited[next]) {
+                count++;
+                dfs(next);
+            }
+        }
+    }
+}