[20251217] BOJ / G5 / 색칠하기 / 이준희

JHLEE325/202512/17 BOJ G5 색칠하기.md

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+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static int N, M;
+    static ArrayList<Integer>[] adj;
+    static int[] colors;
+    static boolean isPossible;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st;
+
+        int T = Integer.parseInt(br.readLine());
+
+        while (T-- > 0) {
+            st = new StringTokenizer(br.readLine());
+            N = Integer.parseInt(st.nextToken());
+            M = Integer.parseInt(st.nextToken());
+
+            adj = new ArrayList[N + 1];
+            for (int i = 1; i <= N; i++) {
+                adj[i] = new ArrayList<>();
+            }
+            colors = new int[N + 1];
+            isPossible = true;
+
+            for (int i = 0; i < M; i++) {
+                st = new StringTokenizer(br.readLine());
+                int u = Integer.parseInt(st.nextToken());
+                int v = Integer.parseInt(st.nextToken());
+
+                adj[u].add(v);
+                adj[v].add(u);
+            }
+
+            for (int i = 1; i <= N; i++) {
+                if (!isPossible) break;
+
+                if (colors[i] == 0) {
+                    bfs(i);
+                }
+            }
+
+            if (isPossible) {
+                System.out.println("possible");
+            } else {
+                System.out.println("impossible");
+            }
+        }
+    }
+
+    private static void bfs(int startNode) {
+        Queue<Integer> queue = new LinkedList<>();
+        queue.add(startNode);
+        colors[startNode] = 1;
+
+        while (!queue.isEmpty()) {
+            int current = queue.poll();
+
+            for (int next : adj[current]) {
+                if (colors[next] == 0) {
+                    colors[next] = 3 - colors[current];
+                    queue.add(next);
+                }
+                else if (colors[next] == colors[current]) {
+                    isPossible = false;
+                    return;
+                }
+            }
+        }
+    }
+}```