[BOJ] 1238 파티 (G3)

Author: uiop5809

박예진/7주차/260211.cpp

@@ -0,0 +1,76 @@
+#include <iostream>
+#include <algorithm>
+#include <vector>
+#include <queue>
+using namespace std;
+
+/*
+  i -> X -> i 왕복하는 최단시간 중 최댓값
+  X -> 모든 노드 (정방향)
+  모든 노드 -> X (역방향)
+*/
+
+struct Node {
+  int node, cost;
+};
+
+struct cmp {
+  bool operator()(const Node &n1, const Node &n2) {
+    return n1.cost > n2.cost; // 오름차순
+  }
+};
+
+int N, X, M;
+vector<vector<Node>> graph;
+vector<vector<Node>> rgraph;
+
+vector<int> dijkstra(int start, vector<vector<Node>> &graph){
+  priority_queue<Node, vector<Node>, cmp> pq; 
+  vector<int> dist(N + 1, 1e9);
+  dist[start] = 0;
+  pq.push({start, dist[start]});
+
+  while(!pq.empty()) {
+    Node now = pq.top();
+    pq.pop();
+
+    if (dist[now.node] < now.cost) continue;
+
+    for(int i = 0; i < graph[now.node].size(); i++){
+      int nextnode = graph[now.node][i].node;
+      int nextcost = graph[now.node][i].cost;
+
+      if (dist[nextnode] > dist[now.node] + nextcost) {
+        dist[nextnode] = dist[now.node] + nextcost;
+        pq.push({nextnode, dist[nextnode]});
+      }
+    }
+  }
+  return dist;
+}
+
+int main() {
+  ios::sync_with_stdio(false);
+  cin.tie(NULL); cout.tie(NULL);
+
+  cin >> N >> M >> X;
+  graph.resize(N + 1);
+  rgraph.resize(N + 1);
+  for(int i = 0; i < M; i++){
+    int a, b, c;
+    cin >> a >> b >> c;
+    graph[a].push_back({b, c});
+    rgraph[b].push_back({a, c});
+  }
+
+  vector<int> v1 = dijkstra(X, graph); // 정방향
+  vector<int> v2 = dijkstra(X, rgraph); // 역방향
+
+  int ans = 0;
+  for(int i = 1; i <= N; i++){
+    ans = max(ans, v1[i] + v2[i]);
+  }
+  cout << ans;
+
+  return 0;
+}