[20250930] PGM / Lv3 / 합승 택시 요금 / 이강현

lkhyun/202509/30 PGM Lv3 합승 택시 요금.md

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+```java
+import java.util.*;
+
+class Solution {
+    static class Edge{
+        int to,cost;
+        Edge(int to, int cost){
+            this.to = to;
+            this.cost = cost;
+        }
+    }
+    static List<Edge>[] adjList;
+    static int[] distA;
+    static int[] distB;
+    static int[] distS;
+    public int solution(int n, int s, int a, int b, int[][] fares) {
+        int answer = 0;
+        adjList = new List[n+1];
+        for(int i = 1; i<=n; i++){
+            adjList[i] = new ArrayList<>();
+        }
+
+        for(int[] fare : fares){
+            adjList[fare[0]].add(new Edge(fare[1],fare[2]));
+            adjList[fare[1]].add(new Edge(fare[0],fare[2]));
+        }
+
+        distA = new int[n+1];
+        distB = new int[n+1];
+        distS = new int[n+1];
+        dijkstra(a,distA);
+        dijkstra(b,distB);
+        dijkstra(s,distS);
+
+        answer = distS[a] + distS[b];
+        for(int i=1; i<=n; i++){
+            answer = Math.min(answer, distS[i] + distA[i] + distB[i]);
+        }
+        return answer;
+    }
+    public void dijkstra(int start, int[] dist){
+        PriorityQueue<Edge> pq = new PriorityQueue<>((a,b) -> Integer.compare(a.cost,b.cost));
+        Arrays.fill(dist, Integer.MAX_VALUE);
+        pq.offer(new Edge(start,0));
+        dist[start] = 0;
+
+        while(!pq.isEmpty()){
+            Edge cur = pq.poll();
+
+            if(dist[cur.to] < cur.cost) continue;
+
+            for(Edge next : adjList[cur.to]){
+                int newDist = cur.cost + next.cost;
+                if(newDist < dist[next.to]){
+                    dist[next.to] = newDist;
+                    pq.offer(new Edge(next.to,newDist));
+                }
+            }
+        }
+    }
+}
+```