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Directed Graph
// src: https://github.com/eugenp/tutorials/blob/5b5733239c06b595649324d744e97c6a2dc97d68/data-structures/src/main/java/com/baeldung/graph/Graph.java
import java.util.ArrayList;
import java.util.List;
import java.util.Stack;
public class Graph {
private List<List<Integer>> neighbours;
private int n;
public Graph(int n) {
this.n = n;
this.neighbours = new ArrayList<List<Integer>>(n);
for (int i = 0; i < n; i++) {
this.neighbours.add(new ArrayList<Integer>());
}
}
public void addEdge(int src, int dest) {
this.neighbours.get(src)
.add(dest);
}
public void dfsWithoutRecursion(int start) {
Stack<Integer> stack = new Stack<Integer>();
boolean[] isVisited = new boolean[n];
stack.push(start);
while (!stack.isEmpty()) {
int current = stack.pop();
isVisited[current] = true;
System.out.print(" " + current);
for (int dest : neighbours.get(current)) {
if (!isVisited[dest])
stack.push(dest);
}
}
}
public void dfs(int start) {
boolean[] isVisited = new boolean[n];
dfsRecursive(start, isVisited);
}
private void dfsRecursive(int current, boolean[] isVisited) {
isVisited[current] = true;
System.out.print(" " + current);
for (int dest : neighbours.get(current)) {
if (!isVisited[dest])
dfsRecursive(dest, isVisited);
}
}
public void topologicalSort(int start) {
Stack<Integer> result = new Stack<Integer>();
boolean[] isVisited = new boolean[n];
topologicalSortRecursive(start, isVisited, result);
while (!result.isEmpty()) {
System.out.print(" " + result.pop());
}
}
private void topologicalSortRecursive(int current, boolean[] isVisited, Stack<Integer> result) {
isVisited[current] = true;
for (int dest : neighbours.get(current)) {
if (!isVisited[dest])
topologicalSortRecursive(dest, isVisited, result);
}
result.push(current);
}
}
//////////
//src: https://github.com/eugenp/tutorials/blob/5b5733239c06b595649324d744e97c6a2dc97d68/data-structures/src/test/java/com/baeldung/graph/GraphUnitTest.java
import org.junit.Test;
public class GraphUnitTest {
@Test
public void givenDirectedGraph_whenDFS_thenPrintAllValues() {
Graph graph = createDirectedGraph();
graph.dfs(0);
System.out.println();
graph.dfsWithoutRecursion(0);
}
@Test
public void givenDirectedGraph_whenGetTopologicalSort_thenPrintValuesSorted() {
Graph graph = createDirectedGraph();
graph.topologicalSort(0);
}
private Graph createDirectedGraph() {
Graph graph = new Graph(6);
graph.addEdge(0, 1);
graph.addEdge(0, 2);
graph.addEdge(1, 3);
graph.addEdge(2, 3);
graph.addEdge(3, 4);
graph.addEdge(4, 5);
return graph;
}
}
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