[20251117] BOJ / G5 / 노드사이의 거리

Author: Ukj0ng

Ukj0ng/202511/17 BOJ G5 노드사이의 거리.md

@@ -0,0 +1,76 @@
+```
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    private static final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    private static List<int[]>[] edges;
+    private static boolean[] visited;
+    private static int N, M;
+    public static void main(String[] args) throws IOException {
+        init();
+
+        while (M-- > 0) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            int start = Integer.parseInt(st.nextToken());
+            int end = Integer.parseInt(st.nextToken());
+
+            bw.write(BFS(start, end) + "\n");
+        }
+
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    private static void init() throws IOException {
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+
+        edges = new List[N+1];
+        visited = new boolean[N+1];
+
+        for (int i = 1; i <= N; i++) {
+            edges[i] = new ArrayList<>();
+        }
+
+        for (int i = 0; i < N-1; i++) {
+            st =  new StringTokenizer(br.readLine());
+            int x = Integer.parseInt(st.nextToken());
+            int y = Integer.parseInt(st.nextToken());
+            int d = Integer.parseInt(st.nextToken());
+
+            edges[x].add(new int[] {y, d});
+            edges[y].add(new int[] {x, d});
+        }
+    }
+
+    private static int BFS(int start, int end) {
+        Queue<int[]> q = new ArrayDeque<>();
+        int result = -1;
+        Arrays.fill(visited, false);
+        visited[start] = true;
+        q.add(new int[] {start, 0});
+
+        while (!q.isEmpty()) {
+            int[] current = q.poll();
+
+            if (current[0] == end) {
+                result = current[1];
+                break;
+            }
+
+            for (int[] edge : edges[current[0]]) {
+                if (visited[edge[0]]) continue;
+
+                visited[edge[0]] = true;
+                q.add(new int[]{edge[0], current[1]+edge[1]});
+            }
+        }
+
+        return result;
+    }
+}
+```