[20250206] BOJ / 실버1 / 지름길 / 이강현

lkhyun/202502/06 BOJ 실버1 지름길.md

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+```java
+import java.util.*;
+import java.io.*;
+
+class Node implements Comparable<Node> {
+    int vertex, weight;
+
+    Node(int vertex, int weight) {
+        this.vertex = vertex;
+        this.weight = weight;
+    }
+
+    @Override
+    public int compareTo(Node n) {
+        return this.weight - n.weight;
+    }
+}
+
+public class Main {
+    final static int INF = Integer.MAX_VALUE;
+    static List<Node>[] graph;
+    static int[] dist;
+
+    public static void dijkstra(int start, int D) {
+        PriorityQueue<Node> minheap = new PriorityQueue<>();
+        Arrays.fill(dist, INF); // 거리 초기화
+        dist[start] = 0;
+        minheap.add(new Node(start, 0));
+
+        while (!minheap.isEmpty()) {
+            Node current = minheap.poll();
+
+            if (current.weight > dist[current.vertex]) continue;
+
+            for (Node next : graph[current.vertex]) {
+                int newWeight = dist[current.vertex] + next.weight;
+                if (dist[next.vertex] > newWeight) {
+                    dist[next.vertex] = newWeight;
+                    minheap.add(new Node(next.vertex, newWeight));
+                }
+            }
+        }
+    }
+
+    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());
+        int N = Integer.parseInt(st.nextToken()); 
+        int D = Integer.parseInt(st.nextToken());
+
+        graph = new ArrayList[D + 1];
+        dist = new int[D + 1];
+        for (int i = 0; i <= D; i++) {
+            graph[i] = new ArrayList<>();
+        }
+
+        for (int i = 0; i < N; i++) {
+            st = new StringTokenizer(br.readLine());
+            int start = Integer.parseInt(st.nextToken());
+            int end = Integer.parseInt(st.nextToken());
+            int weight = Integer.parseInt(st.nextToken());
+
+            if (end <= D && (end - start) > weight) { // 일방통행이니까 목적지보다 더 가거나 굳이 탈 이유가 없는 지름길 제외
+                graph[start].add(new Node(end, weight));
+            }
+        }
+        for (int i = 0; i < D; i++) { //지름길 안타는 경우우
+            graph[i].add(new Node(i + 1, 1));
+        }
+
+        // 다익스트라 실행
+        dijkstra(0, D);
+
+        // 최단 거리 출력
+        bw.write(dist[D] + "\n");
+        bw.flush();
+        bw.close();
+    }
+}
+
+```