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olympiad.java
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olympiad.java
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package kosaraju;
import java.util.*;
public class kosaraju {
public void DFS(List<Integer>[] graph, int v, boolean[] visited, List<Integer> comp) {
visited[v] = true;
for (int i = 0; i < graph[v].size(); i++)
if (!visited[graph[v].get(i)])
DFS(graph, graph[v].get(i), visited, comp);
comp.add(v);
}
public List<Integer> fillOrder(List<Integer>[] graph, boolean[] visited) {
int V = graph.length;
List<Integer> order = new ArrayList<Integer>();
for (int i = 0; i < V; i++)
if (!visited[i])
DFS(graph, i, visited, order);
return order;
}
public List<Integer>[] getTranspose(List<Integer>[] graph) {
int V = graph.length;
List<Integer>[] g = new List[V];
for (int i = 0; i < V; i++)
g[i] = new ArrayList<Integer>();
for (int v = 0; v < V; v++)
for (int i = 0; i < graph[v].size(); i++)
g[graph[v].get(i)].add(v);
return g;
}
public List<List<Integer>> getSCComponents(List<Integer>[] graph) {
int V = graph.length;
boolean[] visited = new boolean[V];
List<Integer> order = fillOrder(graph, visited);
List<Integer>[] reverseGraph = getTranspose(graph);
visited = new boolean[V];
Collections.reverse(order);
/* get all scc */
List<List<Integer>> SCComp = new ArrayList<>();
for (int i = 0; i < order.size(); i++) {
int v = order.get(i);
if (!visited[v]) {
List<Integer> comp = new ArrayList<>();
DFS(reverseGraph, v, visited, comp);
SCComp.add(comp);
}
}
return SCComp;
}
public List<Integer> DFS_depots(List<Integer>[] graph, int v, int t, boolean[] visited, List<Integer> result) {
visited[v] = true;
for (int i = 0; i < graph[v].size(); i++)
{
if (!visited[graph[v].get(i)])
{
DFS_depots(graph, graph[v].get(i), t, visited, result);
}
}
if(visited[t]) {
result.add(0);
}
return result;
}
public List<List<Integer>> findDepots(List<Integer>[] graph, List<List<Integer>> SCC) {
int V = graph.length;
boolean[] visited = new boolean[V];
visited = new boolean[V];
List<Integer> depotsList = new ArrayList<>();
for(int i = 0; i < SCC.size() - 1; i++) {
for(int j = 0; j < SCC.get(i).size(); j++) {
try {
for(int k = 0; k < SCC.get(i + 1).size(); k++) {
int start = SCC.get(i).get(j);
int finish = SCC.get(i + 1).get(k);
System.out.println("Ïðîâåðÿåì: " + start + " -> " + finish);
List<Integer> depots = new ArrayList<>();
depots.clear();
visited = new boolean[V];
DFS_depots(graph, start, finish, visited, depots);
if(!depots.isEmpty()) {
System.out.println("Ðåçóëüòàò: äà, çíà÷èò äåïî áóäåò: " + finish);
depotsList.add(finish);
i++;
depots.clear();
} else {
visited = new boolean[V];
System.out.println("Ðåçóëüòàò: íåò, ïðîâåðÿåì îáðàòíîå");
System.out.println("Ïðîâåðÿåì: " + finish + " -> " + start);
DFS_depots(graph, finish, start, visited, depots);
if(!depots.isEmpty()) {
System.out.println("Ðåçóëüòàò: äà");
System.out.println(depots.get(0));
depots.clear();
} else {
System.out.println("Ðåçóëüòàò: íåò, çíà÷èò äåïî áóäåò: " + finish);
depotsList.add(finish);
depots.clear();
}
}
}
} catch(Exception e) {}
}
}
visited = new boolean[V];
System.out.println("\n- Ïðîâåðêà ìåæäó ïîëó÷åííûìè äåïî: " + depotsList);
List<Integer> finalRecieve = new ArrayList<Integer>();
for(int i = 0; i < depotsList.size() - 1; i++) {
DFS_depots(graph, depotsList.get(i), depotsList.get(i + 1), visited, finalRecieve);
if(finalRecieve.isEmpty()) {
System.out.println("Ñâÿçè " + depotsList.get(i) + " -> " + depotsList.get(i + 1) + " íåò, îñòàâëÿåì êàê åñòü.");
DFS_depots(graph, depotsList.get(i + 1), depotsList.get(i), visited, finalRecieve);
} else {
System.out.println("Ñâÿçü " + depotsList.get(i) + " -> " + depotsList.get(i + 1) + " åñòü, óäàëÿåì " + depotsList.get(i));
depotsList.remove(i);
}
}
System.out.println("Èòîãîâûå äåïî: " + depotsList);
System.out.println("Êîë-âî äåïî: " + depotsList.size());
return SCC;
}
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
kosaraju k = new kosaraju();
System.out.println("Ââåäèòå êîë-âî âåðøèí:");
int V = scan.nextInt();
List<Integer>[] g = new List[V];
for (int i = 0; i < V; i++)
g[i] = new ArrayList<Integer>();
System.out.println("Ââåäèòå êîë-âî ð¸áåð:");
int E = scan.nextInt();
System.out.println("Óêàæèòå " + E + " ñâÿçåé(-è) ìåæäó âåðøèíàìè (V1, V2)");
for (int i = 0; i < E; i++) {
int x = scan.nextInt();
int y = scan.nextInt();
g[x - 1].add(y - 1);
}
List<List<Integer>> scComponents = k.getSCComponents(g);
for(int i = 0; i < scComponents.size(); i++) {
Collections.sort(scComponents.get(i)); }
System.out.println("\n- Êîìïîíåíòû ñèëüíîé ñâÿçè: " + scComponents);
List<List<Integer>> depot = k.findDepots(g, scComponents);
}
}