[20260109] BOJ / G4 / 두 로봇 / 한종욱

Ukj0ng/202601/09 BOJ G4 두 로봇 .md

@@ -0,0 +1,83 @@
+```
+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<Edge>[] edges;
+    private static boolean[] visited;
+    private static int N, start, end;
+
+    public static void main(String[] args) throws IOException {
+        init();
+
+        int answer = BFS();
+
+        bw.write(answer + "\n");
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    private static void init() throws IOException {
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        start = Integer.parseInt(st.nextToken());
+        end = 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 = 1; i < N; i++) {
+            st = new StringTokenizer(br.readLine());
+            int node1 = Integer.parseInt(st.nextToken());
+            int node2 = Integer.parseInt(st.nextToken());
+            int cost = Integer.parseInt(st.nextToken());
+            edges[node1].add(new Edge(node2, cost));
+            edges[node2].add(new Edge(node1, cost));
+        }
+    }
+
+    private static int BFS() {
+        Queue<int[]> q = new ArrayDeque<>();
+        visited[start] = true;
+        int result = 0;
+        // node, cost, max
+        q.add(new int[]{start, 0, 0});
+
+        while (!q.isEmpty()) {
+            int[] current = q.poll();
+
+            if (current[0] == end) {
+                result = current[1]-current[2];
+                break;
+            }
+
+            for (Edge edge : edges[current[0]]) {
+                if (visited[edge.dest]) continue;
+                visited[edge.dest] = true;
+                int cost = current[1] + edge.cost;
+                int max = Math.max(current[2], edge.cost);
+                q.add(new int[]{edge.dest, cost, max});
+            }
+        }
+
+        return result;
+    }
+
+    static class Edge {
+        int dest;
+        int cost;
+
+        public Edge(int dest, int cost) {
+            this.dest = dest;
+            this.cost = cost;
+        }
+    }
+}
+```