18352 특정 거리의 도시 찾기

Author: memory-h

src/main/java/bfs/silver/silver_2/_18352.java

@@ -1,69 +1,79 @@
 package bfs.silver.silver_2;
-import java.io.BufferedReader;
-import java.io.IOException;
-import java.io.InputStreamReader;
-import java.util.ArrayList;
-import java.util.LinkedList;
-import java.util.Queue;
-import java.util.StringTokenizer;
-public class _18352 {
-    static Queue<Integer> q = new LinkedList<>();
-    static ArrayList<ArrayList<Integer>> graph = new ArrayList<>();
 
-    static int[] arr;
-    static boolean check;
-    static int N, M, K, X;
+import java.io.*;
+import java.util.*;
 
-    public static void bfs(int startNode) {
-        arr[startNode] = 0;
-        q.offer(startNode);
+public class _18352 {
 
-        while(!q.isEmpty()) {
-            int n = q.poll();
+    private static int n;
+    private static int m;
+    private static int k;
+    private static int x;
+
+    private static List<List<Integer>> graph;
+    private static List<Integer> nodes;
+    private static boolean[] visited;
 
-            for(int node : graph.get(n)) {
-                if(arr[node] == - 1) {
-                    arr[node] = arr[n] + 1;
-                    q.offer(node);
-                }
-            }
-        }
-    }
     public static void main(String[] args) throws IOException {
         BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
         StringTokenizer st = new StringTokenizer(br.readLine());
+        StringBuilder sb = new StringBuilder();
 
-        N = Integer.parseInt(st.nextToken());	// 도시 개수
-        M = Integer.parseInt(st.nextToken());	// 도로 개수
-        K = Integer.parseInt(st.nextToken());	// 거리 정보
-        X = Integer.parseInt(st.nextToken());	// 출발 도시 번호
+        n = Integer.parseInt(st.nextToken()); // 도시의 개수
+        m = Integer.parseInt(st.nextToken()); // 도로의 개수
+        k = Integer.parseInt(st.nextToken()); // 거리 정보
+        x = Integer.parseInt(st.nextToken()); // 출발 도시의 정보
 
-        arr = new int[N + 1];
+        graph = new ArrayList<>();
+        nodes = new ArrayList<>();
+        visited = new boolean[n + 1];
 
-        for(int i = 0; i < N + 1; i++) {
+        for (int i = 0; i <= n; i++) {
             graph.add(new ArrayList<>());
-            arr[i] = -1;
         }
-        for(int i = 0; i < M; i++) {
+
+        for (int i = 0; i < m; i++) {
             st = new StringTokenizer(br.readLine());
 
             int a = Integer.parseInt(st.nextToken());
             int b = Integer.parseInt(st.nextToken());
 
             graph.get(a).add(b);
         }
-        bfs(X);
 
-        check = false;
+        bfs();
 
-        for(int i = 0; i <= N; i++) {
-            if(arr[i] == K) {
-                System.out.println(i);
-                check = true;
-            }
+        Collections.sort(nodes);
+
+        for (int node : nodes) {
+            sb.append(node).append("\n");
         }
-        if(!check) {
-            System.out.println(-1);
+
+        bw.write(sb.length() == 0 ? "-1" : sb.toString());
+        bw.flush();
+        bw.close();
+    }
+
+    private static void bfs() {
+        Queue<int[]> queue = new LinkedList<>();
+        queue.add(new int[]{x, 0});
+        visited[x] = true;
+
+        while (!queue.isEmpty()) {
+            int[] cur = queue.poll();
+
+            if (cur[1] == k) {
+                nodes.add(cur[0]);
+            }
+
+            for (int next : graph.get(cur[0])) {
+                if (!visited[next]) {
+                    visited[next] = true;
+                    queue.add(new int[]{next, cur[1] + 1});
+                }
+            }
         }
     }
+
 }