[백준 2211] 네트워크 복구 - 최단경로

Author: HiiWee

hoseok/week81/Boj2211.java

@@ -0,0 +1,68 @@
+import java.io.*;
+import java.util.*;
+
+class Main {
+
+    static int n, m;
+    static List<int[]>[] graph;
+    static List<int[]> edges = new ArrayList<>();
+
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        n = Integer.parseInt(st.nextToken());
+        m = Integer.parseInt(st.nextToken());
+        graph = new ArrayList[n + 1];
+
+        for (int i = 0; i <= n; i++) {
+            graph[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());
+            int c = Integer.parseInt(st.nextToken());
+            graph[a].add(new int[]{a, b, c});
+            graph[b].add(new int[]{b, a, c});
+        }
+
+        dijkstra();
+
+        StringBuilder answer = new StringBuilder();
+        answer.append(edges.size()).append("\n");
+        for (int[] edge : edges) {
+            answer.append(edge[0]).append(" ").append(edge[1]).append("\n");
+        }
+        bw.write(answer.toString());
+        bw.flush();
+        bw.close();
+    }
+
+    public static void dijkstra() {
+        int[] dist = new int[n + 1];
+        boolean[] visited = new boolean[n + 1];
+        Arrays.fill(dist, 1_000_000);
+        PriorityQueue<int[]> pq = new PriorityQueue<>(Comparator.comparingInt(o -> o[2]));
+        dist[1] = 0;
+        visited[1] = true;
+        pq.offer(new int[]{1, 1, 0}); // from, to, cost
+
+        while (!pq.isEmpty()) {
+            int[] current = pq.poll();
+
+            if (!visited[current[1]]) {
+                visited[current[1]] = true;
+                edges.add(current);
+            }
+
+            for (int[] next : graph[current[1]]) {
+                if (dist[next[1]] > current[2] + next[2]) {
+                    dist[next[1]] = current[2] + next[2];
+                    pq.offer(new int[]{current[1], next[1], dist[next[1]]});
+                }
+            }
+        }
+    }
+}