[20250926] PGM / LV3 / 부대복귀 / 한종욱

Author: Ukj0ng

Ukj0ng/202509/26 PGM LV3 부대복귀.md

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+```
+import java.util.*;
+
+class Solution {
+    private final int INF = Integer.MAX_VALUE - 10;
+    private List<Integer>[] graph;
+    private int[] dist;
+    
+    public int[] solution(int n, int[][] roads, int[] sources, int destination) {
+        init(n, roads);
+        int[] answer = new int[sources.length];
+        
+        dijkstra(destination);
+        
+        for (int i = 0; i < answer.length; i++) {
+            int result = dist[sources[i]];
+            if (result == INF) answer[i] = -1;
+            else answer[i] = result;
+        }
+        
+        return answer;
+    }
+    
+    private void init(int n, int[][] roads) {
+        graph = new List[n+1];
+        dist = new int[n+1];
+        
+        for (int i = 0; i <= n; i++) {
+            graph[i] = new ArrayList<>();
+        }
+        
+        for (int[] road : roads) {
+            graph[road[0]].add(road[1]);
+            graph[road[1]].add(road[0]);
+        }
+    }
+    
+    private void dijkstra(int start) {
+        PriorityQueue<Node> pq = new PriorityQueue<>((o1, o2) -> Long.compare(o1.cost, o2.cost));
+        Arrays.fill(dist, INF);
+        dist[start] = 0;
+        pq.add(new Node(start, dist[start]));
+        
+        while (!pq.isEmpty()) {
+            Node current = pq.poll();
+            
+            if (current.cost > dist[current.dest]) continue;
+            
+            for (Integer next : graph[current.dest]) {
+                int nCost = 1 + dist[current.dest];
+                
+                if (nCost < dist[next]) {
+                    dist[next] = nCost;
+                    pq.add(new Node(next, dist[next]));
+                }
+            }
+        }
+    }
+    
+    class Node {
+        int dest;
+        int cost;
+        
+        Node (int dest, int cost) {
+            this.dest = dest;
+            this.cost = cost;
+        }
+    }
+}
+```