Section7-12. 그래프 최단거리 (BFS)

Section07/그래프_최단거리_BFS.java

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+package 인프런.Section07;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.Scanner;
+
+public class 그래프_최단거리_BFS {
+    static int n, m;
+    static ArrayList<ArrayList<Integer>> graph;
+    static int[] ch, dis;
+
+    public void BFS(int v) {
+        Queue<Integer> q = new LinkedList<>();
+        ch[v] = 1;
+        dis[v] = 0;
+        q.offer(v);
+
+        while(!q.isEmpty()) {
+            int cv = q.poll();
+            for(int nv : graph.get(cv)) {
+                if(ch[nv] == 0) { //방문 유무
+                    ch[nv] = 1;
+                    q.offer(nv);
+                    dis[nv] = dis[cv] + 1;
+                }
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+
+        그래프_최단거리_BFS t = new 그래프_최단거리_BFS();
+
+        n = scanner.nextInt();
+        m = scanner.nextInt();
+
+        graph = new ArrayList<>();
+        for(int i = 0; i <= n; i++ ){
+            graph.add(new ArrayList<>());
+        }
+
+        ch = new int[n+1];
+        dis = new int[n+1];
+
+        for(int i = 0; i < m; i++) {
+            int a = scanner.nextInt();
+            int b = scanner.nextInt();
+            graph.get(a).add(b);
+        }
+
+        t.BFS(1);
+
+        for(int i = 2; i <= n; i++) {
+            System.out.println(i + " : " + dis[i]);
+        }
+    }
+}