[20250706] BOJ / G2 / 문제집 / 이강현

lkhyun/202507/6 BOJ G2 문제집.md

@@ -0,0 +1,56 @@
+```java
+import java.util.*;
+import java.io.*;
+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 N,M;
+    static List<Integer>[] adj;
+    static int[] degree;
+
+    public static void main(String[] args) throws IOException {
+        st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        adj = new List[N+1];
+        degree = new int[N+1];
+
+        for (int i = 1; i <= N; i++) {
+            adj[i] = new ArrayList<>();
+        }
+
+        for (int i = 0; i < M; i++) {
+            st = new StringTokenizer(br.readLine());
+            int a = Integer.parseInt(st.nextToken());
+            int b = Integer.parseInt(st.nextToken());
+            adj[a].add(b);
+            degree[b]++;
+        }
+
+
+        BFS();
+        bw.close();
+    }
+    static void BFS() throws IOException {
+        PriorityQueue<Integer> pq = new PriorityQueue<>();
+        for (int i = 1; i <= N; i++) {
+            if(degree[i] == 0){
+                pq.add(i);
+            }
+        }
+
+        while(!pq.isEmpty()){
+            int u = pq.poll();
+            bw.write(u+" ");
+
+            for(int v : adj[u]){
+                if(--degree[v] == 0){
+                    pq.add(v);
+                }
+            }
+        }
+    }
+}
+
+```