[20260101] BOJ / G2 / 네트워크 복구 / 김민진

zinnnn37/202601/1 BOJ G2 네트워크 복구.md

@@ -0,0 +1,116 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class BJ_2211_네트워크_복구 {
+
+    private static final int INF = 987654321;
+
+    private static final BufferedReader  br = new BufferedReader(new InputStreamReader(System.in));
+    private static final BufferedWriter  bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    private static final StringBuilder   sb = new StringBuilder();
+    private static       StringTokenizer st;
+
+    private static int N, M;
+    private static int[] dist, parents;
+    private static List<Node>[] graph;
+    private static Queue<Node>  pq;
+    private static Set<String>  set;
+
+    private static class Node implements Comparable<Node> {
+        int to;
+        int weight;
+
+        Node(int to, int weight) {
+            this.to = to;
+            this.weight = weight;
+        }
+
+        @Override
+        public int compareTo(Node o) {
+            return Integer.compare(this.weight, o.weight);
+        }
+
+    }
+
+    public static void main(String[] args) throws IOException {
+        init();
+        sol();
+    }
+
+    private static void init() throws IOException {
+        st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+
+        graph = new List[N + 1];
+        for (int i = 1; i <= N; i++) {
+            graph[i] = new ArrayList<>();
+        }
+
+        dist = new int[N + 1];
+        Arrays.fill(dist, INF);
+
+        parents = new int[N + 1];
+
+        for (int i = 0; i < M; i++) {
+            st = new StringTokenizer(br.readLine());
+
+            int a = Integer.parseInt(st.nextToken());
+            int b = Integer.parseInt(st.nextToken());
+            int c = Integer.parseInt(st.nextToken());
+
+            graph[a].add(new Node(b, c));
+            graph[b].add(new Node(a, c));
+        }
+
+        pq = new PriorityQueue<>();
+        set = new HashSet<>();
+    }
+
+    private static void sol() throws IOException {
+        pq.offer(new Node(1, 0));
+        dist[1] = 0;
+
+        while (!pq.isEmpty()) {
+            Node cur = pq.poll();
+
+            if (cur.weight > dist[cur.to]) continue;
+
+            for (Node next : graph[cur.to]) {
+                int nextWeight = next.weight + dist[cur.to];
+
+                if (nextWeight < dist[next.to]) {
+                    dist[next.to] = nextWeight;
+                    parents[next.to] = cur.to;
+                    pq.offer(new Node(next.to, nextWeight));
+                }
+            }
+        }
+
+        getAns();
+    }
+
+    private static void getAns() throws IOException {
+        for (int i = 1; i <= N; i++) {
+            if (parents[i] == 0) continue;
+
+            int min = Math.min(i, parents[i]);
+            int max = Math.max(i, parents[i]);
+
+            set.add(min + " " + max);
+        }
+
+        sb.append(set.size()).append("\n");
+        for (String s : set) {
+            sb.append(s).append("\n");
+        }
+
+        bw.write(sb.toString());
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+}
+```