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| 1 | +import java.io.BufferedReader; |
| 2 | +import java.io.IOException; |
| 3 | +import java.io.InputStreamReader; |
| 4 | +import java.util.*; |
| 5 | + |
| 6 | +public class SB_1707 { |
| 7 | + static int[] visited; |
| 8 | + static ArrayList<ArrayList<Integer>> adj; |
| 9 | + |
| 10 | + private static boolean bfs(int node) { |
| 11 | + Deque<Integer> que = new ArrayDeque<>(); |
| 12 | + que.offer(node); |
| 13 | + visited[node] = 0; // 처음은 0으로 시작 |
| 14 | + |
| 15 | + while (!que.isEmpty()) { |
| 16 | + int cur = que.poll(); |
| 17 | + for (int nxt : adj.get(cur)) { |
| 18 | + if (visited[nxt] == -1) { |
| 19 | + visited[nxt] = visited[cur] ^ 1; // 다른 팀 배정 |
| 20 | + que.offer(nxt); |
| 21 | + } else if (visited[nxt] == visited[cur]) { |
| 22 | + return false; // 같은 그룹이면 이분 그래프가 아님 |
| 23 | + } |
| 24 | + } |
| 25 | + } |
| 26 | + return true; |
| 27 | + } |
| 28 | + |
| 29 | + public static void main(String[] args) throws IOException { |
| 30 | + BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); |
| 31 | + StringTokenizer st; |
| 32 | + StringBuilder sb = new StringBuilder(); |
| 33 | + |
| 34 | + int K = Integer.parseInt(br.readLine()); |
| 35 | + while (K-- > 0) { |
| 36 | + st = new StringTokenizer(br.readLine()); |
| 37 | + int V = Integer.parseInt(st.nextToken()); |
| 38 | + int E = Integer.parseInt(st.nextToken()); |
| 39 | + |
| 40 | + adj = new ArrayList<>(); |
| 41 | + for (int i = 0; i <= V; i++) { |
| 42 | + adj.add(new ArrayList<>()); |
| 43 | + } |
| 44 | + |
| 45 | + for (int i = 0; i < E; i++) { |
| 46 | + st = new StringTokenizer(br.readLine()); |
| 47 | + int u = Integer.parseInt(st.nextToken()); |
| 48 | + int v = Integer.parseInt(st.nextToken()); |
| 49 | + adj.get(u).add(v); |
| 50 | + adj.get(v).add(u); |
| 51 | + } |
| 52 | + |
| 53 | + visited = new int[V + 1]; |
| 54 | + Arrays.fill(visited, -1); |
| 55 | + |
| 56 | + boolean isBipartite = true; |
| 57 | + for (int i = 1; i <= V; i++) { |
| 58 | + if (visited[i] == -1) { // 방문하지 않은 노드가 있다면 새롭게 탐색 |
| 59 | + if (!bfs(i)) { |
| 60 | + isBipartite = false; |
| 61 | + break; |
| 62 | + } |
| 63 | + } |
| 64 | + } |
| 65 | + |
| 66 | + sb.append(isBipartite ? "YES\n" : "NO\n"); |
| 67 | + } |
| 68 | + |
| 69 | + System.out.print(sb); |
| 70 | + } |
| 71 | +} |
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