[20251009] PGM / LV2 / 배달 / 김수연

suyeun84/202510/09 PGM LV2 배달.md

@@ -0,0 +1,62 @@
+```java
+import java.util.*;
+class Solution {
+    static class Node implements Comparable<Node> {
+        int v, w;
+
+        public Node(int v, int w) {
+            this.v = v;
+            this.w = w;
+        }
+
+        @Override
+        public int compareTo(Node other) {
+            return Integer.compare(this.w, other.w);
+        }
+    }
+
+    public int solution(int N, int[][] road, int K) {        
+        ArrayList<ArrayList<Node>> graph = new ArrayList<>();
+        for (int i = 0; i <= N; i++) {
+            graph.add(new ArrayList<>());
+        }
+
+        for (int i = 0; i < road.length; i++) {
+            int u = road[i][0];
+            int v = road[i][1];
+            int w = road[i][2];
+
+            graph.get(u).add(new Node(v, w));
+            graph.get(v).add(new Node(u, w));
+        }
+
+        int[] dist = new int[N+1];
+        Arrays.fill(dist, Integer.MAX_VALUE);
+        dist[1] = 0;
+
+        PriorityQueue<Node> q = new PriorityQueue<>();
+        q.add(new Node(1, 0));
+
+        while (!q.isEmpty()) {
+            Node current = q.remove();
+
+            if (current.w > dist[current.v]) continue;
+
+            for (Node next : graph.get(current.v)) {
+                int cost = next.w + dist[current.v];
+
+                if (cost < dist[next.v]) {
+                    dist[next.v] = cost;
+                    q.add(new Node(next.v, cost));
+                }
+            }
+        }
+
+        int answer = 0;
+        for (int i = 1; i <= N; i++) {
+            if (dist[i] <= K) answer++;
+        }
+        return answer;
+    }
+}
+```