chore(CSharp): add Depth First Search (#447)
Waqar Hassan Khan
GitHub
parent
f81fabe653
commit
d057b243d9
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@ -18,4 +18,7 @@ For running the `.cs` file please using [.Net Finddle](https://dotnetfiddle.net/
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- [Abundant Number](src/Maths/abundant-number.cs)
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## Recusrsion
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- [Factorial](src/Recursion/factorial.cs)
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- [Factorial](src/Recursion/factorial.cs)
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## Graph
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- [Depth First Search](src/Graph/depth-first-search.cs)
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@ -0,0 +1,131 @@
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using System;
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using System.Collections.Generic;
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using System.Linq;
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namespace Algorithms.Graph
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{
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public class DepthFirstSearch
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{
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class Graph
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{
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private int _vertex;
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private bool _cycleFound;
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private List<List<int>> _adjacencyList;
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private List<int> _parent;
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private List<int> _visited;
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private List<int> _traversal;
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public const int WHITE = 0;
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public const int GREY = 1;
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public const int BLACK = 2;
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public Graph(int vertex)
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{
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_vertex = vertex;
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_traversal = new List<int>();
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_adjacencyList = new List<List<int>>(vertex + 1);
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for (int i = 0; i <= vertex; i++)
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{
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_adjacencyList.Add(new List<int>());
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}
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}
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public void AddEdge(int start, int end)
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{
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_adjacencyList[start].Add(end);
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}
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public List<int> DFS(int source)
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{
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_parent = Enumerable.Repeat(-1, _vertex + 1).ToList();
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_visited = Enumerable.Repeat(WHITE, _vertex + 1).ToList();
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_traversal.Clear();
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DFSRecursive(source);
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return _traversal;
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}
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public bool HasCycle()
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{
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_parent = Enumerable.Repeat(-1, _vertex + 1).ToList();
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_visited = Enumerable.Repeat(WHITE, _vertex + 1).ToList();
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_traversal.Clear();
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DFSRecursive(1);
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return _cycleFound;
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}
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private void DFSRecursive(int source)
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{
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_visited[source] = GREY;
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_traversal.Add(source);
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foreach (int destination in _adjacencyList[source])
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{
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if (_visited[destination] == WHITE)
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{
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_parent[destination] = source;
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DFSRecursive(destination);
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}
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else if (_visited[destination] == GREY && destination != _parent[source])
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{
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_cycleFound = true;
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}
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}
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_visited[source] = BLACK;
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}
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}
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public static List<int> DFS(int vertex, int src, List<Tuple<int, int>> edges)
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{
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Graph graph = new Graph(vertex);
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foreach (var edge in edges)
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{
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graph.AddEdge(edge.Item1, edge.Item2);
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graph.AddEdge(edge.Item2, edge.Item1);
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}
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return graph.DFS(src);
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}
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public static bool HasCycle(int vertex, List<Tuple<int, int>> edges)
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{
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Graph graph = new Graph(vertex);
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foreach (var edge in edges)
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{
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graph.AddEdge(edge.Item1, edge.Item2);
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graph.AddEdge(edge.Item2, edge.Item1);
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}
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return graph.HasCycle();
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}
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public static void Main()
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{
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List<Tuple<int, int>> edges = new List<Tuple<int, int>>();
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edges.Add(new Tuple<int, int>(1, 2));
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edges.Add(new Tuple<int, int>(1, 3));
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edges.Add(new Tuple<int, int>(4, 3));
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edges.Add(new Tuple<int, int>(3, 5));
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List<int> traversal = DFS(5, 1, edges);
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foreach (int v in traversal)
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{
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Console.Write($"{v} ");
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}
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Console.WriteLine($"Has Cycle: {HasCycle(5, edges)}");
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}
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}
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}
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/*
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* depth first search for an undirected graph
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* also cycles are detected
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*/
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@ -0,0 +1,64 @@
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using System;
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using NUnit.Framework;
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using System.Collections.Generic;
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namespace Algorithms.Tests.Graph
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{
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[TestFixture]
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public class DepthFirstSearch
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{
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static object[] DivideCasesForDFS =
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{
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new object[] { 5, 3, new List<Tuple<int, int>> {
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new Tuple<int, int>(1, 2),
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new Tuple<int, int>(1, 3),
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new Tuple<int, int>(2, 3),
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new Tuple<int, int>(4, 2),
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new Tuple<int, int>(1, 5)
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}, "3 1 2 4 5"
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},
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new object[] { 5, 1, new List<Tuple<int, int>> {
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new Tuple<int, int>(1, 2),
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new Tuple<int, int>(1, 3),
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new Tuple<int, int>(4, 3),
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new Tuple<int, int>(3, 5)
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}, "1 2 3 4 5"
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}
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};
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static object[] DivideCasesForCycleDetection =
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{
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new object[] { 5, new List<Tuple<int, int>> {
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new Tuple<int, int>(1, 2),
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new Tuple<int, int>(1, 3),
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new Tuple<int, int>(2, 3),
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new Tuple<int, int>(4, 2),
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new Tuple<int, int>(1, 5)
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}, true
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},
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new object[] { 5, new List<Tuple<int, int>> {
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new Tuple<int, int>(1, 2),
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new Tuple<int, int>(1, 3),
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new Tuple<int, int>(4, 3),
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new Tuple<int, int>(3, 5)
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}, false
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}
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};
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[TestCaseSource(nameof(DivideCasesForDFS))]
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public void TestDFS_ShouldGetExpectedResult(int vertex, int source, List<Tuple<int, int>> edges, string expected)
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{
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List<int> result = Algorithms.Graph.DepthFirstSearch.DFS(vertex, source, edges);
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Assert.AreEqual(expected, string.Join(' ', result));
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}
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[TestCaseSource(nameof(DivideCasesForCycleDetection))]
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public void TestCycleDetection_ShouldGetExpectedResult(int vertex, List<Tuple<int, int>> edges, bool expected)
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{
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bool result = Algorithms.Graph.DepthFirstSearch.HasCycle(vertex, edges);
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Assert.AreEqual(expected, result);
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}
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}
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}
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