Create [16]_2.cpp

Author: ndb796

Solutions/[16]_2.cpp

@@ -0,0 +1,80 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, m, start, finish;
+vector<pair<int, int> > adj[500];
+int d[500];
+vector<pair<int, int> > reverseAdj[500];
+bool dropped[500][500];
+
+void dijkstra() {
+	priority_queue<pair<int, int> > pq;
+	pq.push(make_pair(0, start));
+	d[start] = 0;
+	while (!pq.empty()) {
+		int dist = -pq.top().first; // 현재 노드까지의 비용 
+		int now = pq.top().second; // 현재 노드 
+		pq.pop();
+		if (d[now] < dist) continue;
+		for (int i = 0; i < adj[now].size(); i++) {
+			int next = adj[now][i].first; // 다음 노드 
+			int nextDist = dist + adj[now][i].second; // 현재 노드를 거쳐 가는 비용 
+			if (d[next] > nextDist && !dropped[now][next]) {
+				d[next] = nextDist;
+				pq.push(make_pair(-nextDist, next));
+			}
+		}
+	}
+}
+
+void bfs() {
+	queue<int> q;
+	q.push(finish);
+	while (!q.empty()) {
+		int now = q.front();
+		q.pop();
+		if (now == start) continue;
+		for (int i = 0; i < reverseAdj[now].size(); i++) {
+			int prev = reverseAdj[now][i].first;
+			int cost = reverseAdj[now][i].second;
+			// 최단 경로에 포함된 경우 체크하기 
+			if (d[now] == d[prev] + cost) {
+				dropped[prev][now] = true;
+				q.push(prev);
+			}
+		}
+	}
+}
+
+int main() {
+	while (true) {
+		cin >> n >> m;
+		if (n == 0) break;
+		cin >> start >> finish;
+		for (int i = 0; i < n; i++) {
+			adj[i].clear();
+			reverseAdj[i].clear();
+		}
+		for (int i = 0; i < m; i++) {
+			int x, y, cost;
+			cin >> x >> y >> cost;
+			adj[x].push_back(make_pair(y, cost));
+			reverseAdj[y].push_back(make_pair(x, cost));
+		}
+		// false로 초기화할 때는 memset() 함수 이용 
+		memset(dropped, false, sizeof(dropped));
+		// 특정한 값으로 초기화할 때는 fill() 함수 이용 
+		fill(d, d + 500, 1e9);
+		dijkstra();
+		bfs();
+		fill(d, d + 500, 1e9);
+		dijkstra();
+		if (d[finish] != 1e9) {
+			cout << d[finish] << '\n';
+		}
+		else {
+			cout << -1 << '\n';
+		}
+	}
+}