JavaAlgorithms/DataStructures/Graphs/Cycles.java

package DataStructures.Graphs;

import java.util.ArrayList;
import java.util.Scanner;

class Cycle {

  private int nodes, edges;
  private int[][] adjacencyMatrix;
  private boolean[] visited;
  ArrayList<ArrayList<Integer>> cycles = new ArrayList<ArrayList<Integer>>();

  public Cycle() {
    Scanner in = new Scanner(System.in);
    System.out.print("Enter the no. of nodes: ");
    nodes = in.nextInt();
    System.out.print("Enter the no. of Edges: ");
    edges = in.nextInt();

    adjacencyMatrix = new int[nodes][nodes];
    visited = new boolean[nodes];

    for (int i = 0; i < nodes; i++) {
      visited[i] = false;
    }

    System.out.println("Enter the details of each edges <Start Node> <End Node>");

    for (int i = 0; i < edges; i++) {
      int start, end;
      start = in.nextInt();
      end = in.nextInt();
      adjacencyMatrix[start][end] = 1;
    }
    in.close();
  }

  public void start() {
    for (int i = 0; i < nodes; i++) {
      ArrayList<Integer> temp = new ArrayList<>();
      dfs(i, i, temp);
      for (int j = 0; j < nodes; j++) {
        adjacencyMatrix[i][j] = 0;
        adjacencyMatrix[j][i] = 0;
      }
    }
  }

  private void dfs(Integer start, Integer curr, ArrayList<Integer> temp) {
    temp.add(curr);
    visited[curr] = true;
    for (int i = 0; i < nodes; i++) {
      if (adjacencyMatrix[curr][i] == 1) {
        if (i == start) {
          cycles.add(new ArrayList<Integer>(temp));
        } else {
          if (!visited[i]) {
            dfs(start, i, temp);
          }
        }
      }
    }

    if (temp.size() > 0) {
      temp.remove(temp.size() - 1);
    }
    visited[curr] = false;
  }

  public void printAll() {
    for (int i = 0; i < cycles.size(); i++) {
      for (int j = 0; j < cycles.get(i).size(); j++) {
        System.out.print(cycles.get(i).get(j) + " -> ");
      }
      System.out.println(cycles.get(i).get(0));
      System.out.println();
    }
  }
}

public class Cycles {
  public static void main(String[] args) {
    Cycle c = new Cycle();
    c.start();
    c.printAll();
  }
}