[20250831] BOJ / G5 / 노드사이의 거리 / 이인희

LiiNi-coder/202508/31 BOJ 노드사이의 거리.md

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+```java
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.PriorityQueue;
+import java.util.StringTokenizer;
+
+public class Main {
+    private static BufferedReader Br;
+    private static BufferedWriter Bw;
+    private static StringBuilder Sb;
+    private static int N;
+    private static int M;
+    private static List<Node>[] Graph;
+
+    private static class Node implements Comparable<Node> {
+        int v;
+        int w;
+        public Node(int v, int w) {
+            this.v = v;
+            this.w = w;
+        }
+        @Override
+        public int compareTo(Node o) {
+            return this.w - o.w;
+        }
+    }
+
+    public static void main(String[] args) throws IOException {
+        Br = new BufferedReader(new InputStreamReader(System.in));
+        Bw = new BufferedWriter(new OutputStreamWriter(System.out));
+        Sb = new StringBuilder();
+        StringTokenizer st = new StringTokenizer(Br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        Graph = new ArrayList[N + 1];
+        for (int i = 1; i <= N; i++) {
+            Graph[i] = new ArrayList<>();
+        }
+        for (int i = 0; i < N - 1; i++) {
+            st = new StringTokenizer(Br.readLine());
+            int a = Integer.parseInt(st.nextToken());
+            int b = Integer.parseInt(st.nextToken());
+            int w = Integer.parseInt(st.nextToken());
+            Graph[a].add(new Node(b, w));
+            Graph[b].add(new Node(a, w));
+        }
+        for (int i = 0; i < M; i++) {
+            st = new StringTokenizer(Br.readLine());
+            int s = Integer.parseInt(st.nextToken());
+            int e = Integer.parseInt(st.nextToken());
+            Sb.append(dijkstra(s, e)).append("\n");
+        }
+        Bw.write(Sb.toString());
+        Bw.flush();
+        Bw.close();
+        Br.close();
+    }
+
+    private static int dijkstra(int start, int end) {
+        int[] dist = new int[N + 1];
+        for (int i = 1; i <= N; i++)
+            dist[i] = Integer.MAX_VALUE;
+        PriorityQueue<Node> pq = new PriorityQueue<>();
+        pq.add(new Node(start, 0));
+        dist[start] = 0;
+        while (!pq.isEmpty()) {
+            Node cur = pq.poll();
+            if (dist[cur.v] < cur.w) continue;
+            if (cur.v == end) return cur.w;
+
+            for (Node next : Graph[cur.v]) {
+                if (dist[next.v] > cur.w + next.w) {
+                    dist[next.v] = cur.w + next.w;
+                    pq.add(new Node(next.v, dist[next.v]));
+                }
+            }
+        }
+        return -1;
+    }
+}
+
+```