[20250905] BOJ / G4 / 이분 그래프 / 한종욱

Ukj0ng/202509/5 BOJ G4 이분 그래프.md

@@ -0,0 +1,81 @@
+```
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    private static final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    private static List<Integer>[] graph;
+    private static int[] visited;
+    private static int V, E;
+
+    public static void main(String[] args) throws IOException {
+        int K = Integer.parseInt(br.readLine());
+
+        while (K-- > 0) {
+            init();
+
+            boolean result = true;
+
+            for (int i = 1; i <= V; i++) {
+                if (visited[i] == 0) {
+                    result = BFS(i);
+                }
+
+                if (!result) break;
+            }
+
+            if (result) bw.write("YES" + "\n");
+            else bw.write("NO" + "\n");
+        }
+
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    private static void init() throws IOException {
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        V = Integer.parseInt(st.nextToken());
+        E = Integer.parseInt(st.nextToken());
+
+        visited = new int[V + 1];
+        graph = new List[V + 1];
+
+        for (int i = 0; i <= V; i++) {
+            graph[i] = new ArrayList<>();
+        }
+
+        for (int i = 0; i < E; i++) {
+            st = new StringTokenizer(br.readLine());
+
+            int a = Integer.parseInt(st.nextToken());
+            int b = Integer.parseInt(st.nextToken());
+
+            graph[a].add(b);
+            graph[b].add(a);
+        }
+    }
+
+    private static boolean BFS(int start) {
+        Queue<Integer> q = new ArrayDeque<>();
+        visited[start] = 1;
+        q.add(start);
+
+        while (!q.isEmpty()) {
+            int current = q.poll();
+
+            for (int next : graph[current]) {
+                if (visited[next] == visited[current]) return false;
+
+                if (visited[next] == 0) {
+                    visited[next] = 3 - visited[current];
+                    q.add(next);
+                }
+            }
+        }
+
+        return true;
+    }
+}
+```