[20250824] BOJ / G4 / 이분 그래프 / 이준희

JHLEE325/202508/24 BOJ G4 이분 그래프.md

@@ -0,0 +1,75 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    static ArrayList<Integer>[] graph;
+    static int[] color;
+    static int v, e;
+
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st;
+        StringBuilder sb = new StringBuilder();
+        int T = Integer.parseInt(br.readLine());
+
+        for (int t = 0; t < T; t++) {
+            st = new StringTokenizer(br.readLine());
+            v = Integer.parseInt(st.nextToken());
+            e = Integer.parseInt(st.nextToken());
+
+            graph = new ArrayList[v + 1];
+            for (int i = 1; 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);
+            }
+
+            color = new int[v + 1];
+            boolean ok = true;
+
+            for (int i = 1; i <= v && ok; i++) {
+                if (color[i] == 0) {
+                    ok = bfs(i);
+                }
+            }
+
+            if(ok){
+                sb.append("YES\n");
+            }
+            else{
+                sb.append("NO\n");
+            }
+        }
+
+        System.out.print(sb.toString());
+    }
+
+    static boolean bfs(int s) {
+        ArrayDeque<Integer> q = new ArrayDeque<>();
+        color[s] = 1;
+        q.offer(s);
+
+        while (!q.isEmpty()) {
+            int u = q.poll();
+            int nextColor = -color[u];
+
+            for (int v : graph[u]) {
+                if (color[v] == 0) {
+                    color[v] = nextColor;
+                    q.offer(v);
+                } else if (color[v] == color[u]) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
+
+```