[20250914] BOJ / G4 / 이분 그래프 / 이강현

Author: lkhyun

lkhyun/202509/14 BOJ G4 이분 그래프.md

@@ -0,0 +1,68 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    static StringTokenizer st;
+    static int K;
+    static int V, E;
+    static List<Integer>[] adjLists;
+
+    public static void main(String[] args) throws IOException {
+        K = Integer.parseInt(br.readLine());
+        
+        for (int i = 0; i < K; i++) {
+            st = new StringTokenizer(br.readLine());
+            V = Integer.parseInt(st.nextToken());
+            E = Integer.parseInt(st.nextToken());
+            adjLists = new List[V + 1];
+            for (int j = 1; j <= V; j++) {
+                adjLists[j] = new ArrayList<>();
+            }
+            for (int j = 0; j < E; j++) {
+                st = new StringTokenizer(br.readLine());
+                int u = Integer.parseInt(st.nextToken());
+                int v = Integer.parseInt(st.nextToken());
+                adjLists[u].add(v);
+                adjLists[v].add(u);
+            }
+            if (!BFS()) {
+                bw.write("NO\n");
+            } else {
+                bw.write("YES\n");
+            }
+        }
+        bw.close();
+    }
+
+    public static boolean BFS() {
+        ArrayDeque<Integer> q = new ArrayDeque<>();
+        int[] visited = new int[V+1];
+        
+        for (int i = 1; i <= V; i++) {
+            if (visited[i] == 0) {  
+                q.offer(i);
+                visited[i] = 1;  
+                
+                while (!q.isEmpty()) {
+                    int cur = q.poll();
+                    
+                    for (int next : adjLists[cur]) {
+                        if (visited[next] == 0) {
+                            visited[next] = -visited[cur];
+                            q.offer(next);
+                        } else if (visited[next] == visited[cur]) {
+                            
+                            return false;
+                        }
+                    }
+                }
+            }
+        }
+        return true;
+    }
+}
+
+```