260126 : [BOJ 11780] 플로이드 2

_munhyeong/11780.cpp

@@ -0,0 +1,103 @@
+#include <algorithm>
+#include <iostream>
+#include <vector>
+#define INF 987654321
+
+using namespace std;
+
+struct Info {
+	int cost;
+	int vertex;
+};
+
+void print(vector<vector<int>>& graph) {
+	for (int i = 0; i < graph.size(); i++) {
+		for (int j = 0; j < graph.size(); j++) {
+			cout << graph[i][j] << " ";
+		}
+		cout << "\n";
+	}
+	cout << "\n";
+}
+
+void find_path(vector<vector<Info>>& graph, vector<int>& path, int from, int to) {
+	int mid = graph[from][to].vertex;
+	if (from == mid || mid == -1) {
+		path.push_back(from);
+		return;
+	}
+	find_path(graph, path, from, mid);
+	find_path(graph, path, mid, to);
+}
+
+int main() {
+	int n, m;
+	cin >> n >> m;
+
+	vector<vector<Info>> graph(n, vector<Info>(n, { INF, -1 }));
+	for (int i = 0; i < m; i++) {
+		int a, b, cost;
+		cin >> a >> b >> cost;
+
+		a--; b--;
+		if (graph[a][b].cost > cost) {
+			graph[a][b] = { cost, a };
+		}
+	}
+
+	for (int i = 0; i < n; i++) {
+		graph[i][i].cost = 0;
+	}
+
+
+	// 플로이드 와샬 코드인데
+	// 역추적을 어떻게 하면 되는거지?
+	for (int mid = 0; mid < n; mid++) {
+		for (int start = 0; start < n; start++) {
+			for (int end = 0; end < n; end++) {
+				if (graph[start][end].cost > graph[start][mid].cost + graph[mid][end].cost) {
+					graph[start][end].cost = graph[start][mid].cost + graph[mid][end].cost;
+					graph[start][end].vertex = mid; // start-end까지 가는데 mid를 거치는게 빠름
+				}
+			}
+		}
+	}
+
+	for (int i = 0; i < n; i++) {
+		for (int j = 0; j < n; j++) {
+			cout << ((graph[i][j].cost != INF) ? graph[i][j].cost : 0) << " ";
+		}
+		cout << "\n";
+	}
+	/*// === [DEBUG] ===
+	cout << "\n";
+	for (int i = 0; i < n; i++) {
+		for (int j = 0; j < n; j++) {
+			cout << graph[i][j].vertex << " ";
+		}
+		cout << "\n";
+	}
+	cout << "\n";
+	// === [DEBUG] === */
+
+	for (int i = 0; i < n; i++) {
+		for (int j = 0; j < n; j++) {
+			if (i == j || graph[i][j].cost == INF) {
+				cout << 0 << "\n";
+				continue;
+			}
+
+			vector<int> answer;
+			find_path(graph, answer, i, j);
+			answer.push_back(j);
+
+			cout << answer.size() << " ";
+			for (auto e : answer)
+				cout << e + 1 << " ";
+			cout << "\n";
+		}
+		//cout << "\n";
+	}
+
+	return 0;
+}