113 lines
3.1 KiB
Java
113 lines
3.1 KiB
Java
import java.util.*;
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public class WeaklyConnectedGraph
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{
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private int V;
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private int preCount;
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private int[] low;
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private boolean[] visited;
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private List<Integer>[] graph;
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private List<List<Integer>> sccComp;
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private Stack<Integer> stack;
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/** function to get all strongly connected components **/
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public List<List<Integer>> getSCComponents(List<Integer>[] graph)
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{
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V = graph.length;
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this.graph = graph;
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low = new int[V];
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visited = new boolean[V];
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stack = new Stack<Integer>();
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sccComp = new ArrayList<>();
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for (int v = 0; v < V; v++)
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if (!visited[v])
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dfs(v);
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return sccComp;
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}
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/** function dfs **/
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public void dfs(int v)
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{
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low[v] = preCount++;
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visited[v] = true;
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stack.push(v);
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int min = low[v];
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for (int w : graph[v])
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{
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if (!visited[w])
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dfs(w);
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if (low[w] < min)
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min = low[w];
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}
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if (min < low[v])
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{
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low[v] = min;
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return;
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}
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List<Integer> component = new ArrayList<Integer>();
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int w;
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do
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{
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w = stack.pop();
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component.add(w);
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low[w] = V;
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}
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while (w != v);
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sccComp.add(component);
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}
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@SuppressWarnings("unchecked")
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public static void main(String[] args)
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{
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Scanner scan = new Scanner(System.in);
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System.out.println("Enter number of Vertices");
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/** number of vertices **/
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int V = scan.nextInt();
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/** make graph **/
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List<Integer>[] g = new List[V];
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for (int i = 0; i < V; i++)
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g[i] = new ArrayList<Integer>();
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/** accept all edges **/
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System.out.println("Enter number of edges");
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int E = scan.nextInt();
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/** all edges **/
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System.out.println("Enter the edges in the graph : <from> <to>");
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for (int i = 0; i < E; i++)
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{
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int x = scan.nextInt();
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int y = scan.nextInt();
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g[x].add(y);
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}
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StronglyConnectedGraph t = new StronglyConnectedGraph();
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System.out.print("The graph is weakly connected? : ");
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/** print all strongly connected components **/
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List<List<Integer>> scComponents = t.getSCComponents(g);
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Iterator<List<Integer>> iterator = scComponents.iterator();
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boolean weaklyConnected = false;
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while (iterator.hasNext())
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{
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if (iterator.next().size() <= 1)
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{
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weaklyConnected = true;
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}
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}
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System.out.println(weaklyConnected);
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scan.close();
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}
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}
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/*
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Enter number of Vertices
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6
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Enter number of edges
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7
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Enter the edges in the graph : <from> <to>
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0 1
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1 2
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1 3
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3 4
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4 5
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5 3
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5 2
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The graph is weakly connected? : true |