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Merge pull request #1815 from Kumar-laxmi/pilot
Push Kosaraju's Algorithm in Java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,113 @@ | ||
| import java.util.ArrayList; | ||
| import java.util.List; | ||
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| class GFG { | ||
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| // dfs Function to reach destination | ||
| boolean dfs(int curr, int des, List<List<Integer>> adj, | ||
| List<Integer> vis) { | ||
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| // If curr node is destination return true | ||
| if (curr == des) { | ||
| return true; | ||
| } | ||
| vis.set(curr, 1); | ||
| for (int x : adj.get(curr)) { | ||
| if (vis.get(x) == 0) { | ||
| if (dfs(x, des, adj, vis)) { | ||
| return true; | ||
| } | ||
| } | ||
| } | ||
| return false; | ||
| } | ||
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| // To tell whether there is path from source to | ||
| // destination | ||
| boolean isPath(int src, int des, List<List<Integer>> adj) { | ||
| List<Integer> vis = new ArrayList<>(adj.size() + 1); | ||
| for (int i = 0; i <= adj.size(); i++) { | ||
| vis.add(0); | ||
| } | ||
| return dfs(src, des, adj, vis); | ||
| } | ||
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| // Function to return all the strongly connected | ||
| // component of a graph. | ||
| List<List<Integer>> findSCC(int n, List<List<Integer>> a) { | ||
| // Stores all the strongly connected components. | ||
| List<List<Integer>> ans = new ArrayList<>(); | ||
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| // Stores whether a vertex is a part of any Strongly | ||
| // Connected Component | ||
| List<Integer> is_scc = new ArrayList<>(n + 1); | ||
| for (int i = 0; i <= n; i++) { | ||
| is_scc.add(0); | ||
| } | ||
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| List<List<Integer>> adj = new ArrayList<>(); | ||
| for (int i = 0; i <= n; i++) { | ||
| adj.add(new ArrayList<>()); | ||
| } | ||
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| for (List<Integer> edge : a) { | ||
| adj.get(edge.get(0)).add(edge.get(1)); | ||
| } | ||
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| // Traversing all the vertices | ||
| for (int i = 1; i <= n; i++) { | ||
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| if (is_scc.get(i) == 0) { | ||
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| // If a vertex i is not a part of any SCC | ||
| // insert it into a new SCC list and check | ||
| // for other vertices whether they can be | ||
| // the part of this list. | ||
| List<Integer> scc = new ArrayList<>(); | ||
| scc.add(i); | ||
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| for (int j = i + 1; j <= n; j++) { | ||
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| // If there is a path from vertex i to | ||
| // vertex j and vice versa, put vertex j | ||
| // into the current SCC list. | ||
| if (is_scc.get(j) == 0 && isPath(i, j, adj) | ||
| && isPath(j, i, adj)) { | ||
| is_scc.set(j, 1); | ||
| scc.add(j); | ||
| } | ||
| } | ||
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| // Insert the SCC containing vertex i into | ||
| // the final list. | ||
| ans.add(scc); | ||
| } | ||
| } | ||
| return ans; | ||
| } | ||
| } | ||
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| public class Main { | ||
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| public static void main(String[] args) { | ||
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| GFG obj = new GFG(); | ||
| int V = 5; | ||
| List<List<Integer>> edges = new ArrayList<>(); | ||
| edges.add(new ArrayList<>(List.of(1, 3))); | ||
| edges.add(new ArrayList<>(List.of(1, 4))); | ||
| edges.add(new ArrayList<>(List.of(2, 1))); | ||
| edges.add(new ArrayList<>(List.of(3, 2))); | ||
| edges.add(new ArrayList<>(List.of(4, 5))); | ||
| List<List<Integer>> ans = obj.findSCC(V, edges); | ||
| System.out.println("Strongly Connected Components are:"); | ||
| for (List<Integer> x : ans) { | ||
| for (int y : x) { | ||
| System.out.print(y + " "); | ||
| } | ||
| System.out.println(); | ||
| } | ||
| } | ||
| } | ||
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| // This code is contributed by shivamgupta310570 |
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