solved 이분 그래프 - 836ms 271424KB

Baekjoon/이분그래프/이분그래프_강정훈.java

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+import java.io.*;
+import java.util.*;
+
+class Main {
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int K = Integer.parseInt(br.readLine());
+        for (int T = 0; T < K; T++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            int V = Integer.parseInt(st.nextToken());
+            int E = Integer.parseInt(st.nextToken());
+            List<Integer>[] graph = new ArrayList[V + 1];
+            for (int index = 0; index < V + 1; index++) {
+                graph[index] = new ArrayList<>();
+            }
+            for (int index = 0; index < E; index++) {
+                st = new StringTokenizer(br.readLine());
+                int start = Integer.parseInt(st.nextToken());
+                int end = Integer.parseInt(st.nextToken());
+                graph[start].add(end);
+                graph[end].add(start);
+            }
+
+            if (isBinaryGraph(graph, V)) {
+                System.out.println("YES");
+            } else {
+                System.out.println("NO");
+            }
+        }
+    }
+
+    private static boolean isBinaryGraph(List<Integer>[] graph, int V) {
+        int[] groups = new int[V + 1];
+        for (int initialNode = 1; initialNode <= V; initialNode++) {
+            if (groups[initialNode] != 0) {
+                continue;
+            }
+            Queue<Integer> q = new ArrayDeque<>();
+            groups[initialNode] = 1;
+            q.add(initialNode);
+            while (!q.isEmpty()) {
+                int current = q.poll();
+                for (int nextIndex : graph[current]) {
+                    if (groups[current] == groups[nextIndex]) {
+                        return false;
+                    }
+                    if (groups[nextIndex] == 0) {
+                        groups[nextIndex] = groups[current] * (-1);
+                        q.add(nextIndex);
+                    }
+                }
+            }
+        }
+        return true;
+    }
+}