[최단경로] 2176251이민경

13_최단 경로/필수/boj1238.cpp

@@ -0,0 +1,67 @@
+#include <iostream>
+#include <vector>
+#include <queue>
+
+using namespace std;
+typedef pair<int, int> ci;
+const int INF = 1e9; // 무한대 값
+
+vector<int> dijkstra(int start, int v, vector<vector<ci>>& graph) {
+    vector<int> dist(v + 1, INF);
+    priority_queue<ci, vector<ci>, greater<>> pq;
+
+    dist[start] = 0;
+    pq.push({ 0, start });
+
+    while (!pq.empty()) {
+        int weight = pq.top().first;
+        int node = pq.top().second;
+        pq.pop();
+
+        if (weight > dist[node]) {
+            continue;
+        }
+
+        for (int i = 0; i < graph[node].size(); i++) {
+            int next_node = graph[node][i].first;
+            int next_weight = weight + graph[node][i].second;
+
+            if (next_weight < dist[next_node]) {
+                dist[next_node] = next_weight;
+                pq.push({ next_weight, next_node });
+            }
+        }
+    }
+
+    return dist;
+}
+
+int main() {
+    int n, m, x;
+    cin >> n >> m >> x;
+
+    vector<vector<ci>> graph(n + 1, vector<ci>(0));
+    vector<vector<ci>> reverse_graph(n + 1, vector<ci>(0)); // 역방향 그래프 생성
+
+    for (int i = 0; i < m; i++) {
+        int a, b, t;
+        cin >> a >> b >> t;
+        graph[a].push_back({ b, t });
+        reverse_graph[b].push_back({ a, t }); // 역방향 그래프에 추가
+    }
+
+    vector<int> forward_dist = dijkstra(x, n, graph); // X에서 각 마을로 가는 최단 시간
+    vector<int> reverse_dist = dijkstra(x, n, reverse_graph); // 각 마을에서 X로 돌아오는 최단 시간
+
+    int max_time = 0;
+    for (int i = 1; i <= n; i++) {
+        if (i == x) continue;
+        int total_time = forward_dist[i] + reverse_dist[i]; // 왕복시간 계산
+        max_time = max(max_time, total_time);
+    }
+
+    cout << max_time << endl;
+
+    return 0;
+}
+/*hi*/