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Commit ef38be4

Browse files
Clean up combinatorics
1 parent c5ef69b commit ef38be4

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4 files changed

+29
-11
lines changed

4 files changed

+29
-11
lines changed

‎src/Advanced.Algorithms/Combinatorics/Combination.cs

Lines changed: 5 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1,17 +1,18 @@
1-
using System.Collections.Generic;
1+
using System;
2+
using System.Collections.Generic;
23

34
namespace Advanced.Algorithms.Combinatorics
45
{
56
/// <summary>
6-
/// Combinations computer.
7+
/// Combination generator (nCr).
78
/// </summary>
89
public class Combination
910
{
10-
public static List<List<T>> Find<T>(List<T> input, int r, bool withRepetition)
11+
public static List<List<T>> Find<T>(List<T> n, int r, bool withRepetition=false)
1112
{
1213
var result = new List<List<T>>();
1314

14-
recurse(input, r, withRepetition, 0, new List<T>(), new HashSet<int>(), result);
15+
recurse(n, r, withRepetition, 0, new List<T>(), new HashSet<int>(), result);
1516

1617
return result;
1718
}

‎src/Advanced.Algorithms/Combinatorics/Permutation.cs

Lines changed: 5 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1,17 +1,18 @@
1-
using System.Collections.Generic;
1+
using System;
2+
using System.Collections.Generic;
23

34
namespace Advanced.Algorithms.Combinatorics
45
{
56
/// <summary>
6-
/// Permutation computer.
7+
/// Permutation generator (nPr).
78
/// </summary>
89
public class Permutation
910
{
10-
public static List<List<T>> Find<T>(List<T> input, int r, bool withRepetition = false)
11+
public static List<List<T>> Find<T>(List<T> n, int r, bool withRepetition = false)
1112
{
1213
var result = new List<List<T>>();
1314

14-
recurse(input, r, withRepetition, new List<T>(), new HashSet<int>(), result);
15+
recurse(n, r, withRepetition, new List<T>(), new HashSet<int>(), result);
1516

1617
return result;
1718
}

‎src/Advanced.Algorithms/Combinatorics/Subset.cs

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
namespace Advanced.Algorithms.Combinatorics
44
{
55
/// <summary>
6-
/// Subset computer.
6+
/// Subset generator.
77
/// </summary>
88
public class Subset
99
{
@@ -32,7 +32,7 @@ private static void recurse<T>(List<T> input,
3232
prefix.Add(input[j]);
3333
prefixIndices.Add(j);
3434

35-
recurse(input, j, prefix, prefixIndices, result);
35+
recurse(input, j+1, prefix, prefixIndices, result);
3636

3737
prefix.RemoveAt(prefix.Count - 1);
3838
prefixIndices.Remove(j);

‎tests/Advanced.Algorithms.Tests/Combinatorics/Combination_Tests.cs

Lines changed: 17 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,7 @@ public class Combination_Tests
1414

1515
//for verification
1616
static readonly Func<int, int, int> combination = (int n, int r)
17-
=> n == 0 ||r==0? 0 : factorial(n) / (factorial(r) * factorial(n - r));
17+
=> n == 0 ? 0 : factorial(n) / (factorial(r) * factorial(n - r));
1818

1919
[TestMethod]
2020
public void Combination_Without_Repetitions_Smoke_Test()
@@ -30,6 +30,14 @@ public void Combination_Without_Repetitions_Smoke_Test()
3030
input = "monster".ToCharArray().ToList();
3131
combinations = Combination.Find<char>(input, 4, false);
3232
Assert.AreEqual(combination(input.Count, 4), combinations.Count);
33+
34+
input = "pen".ToCharArray().ToList();
35+
combinations = Combination.Find<char>(input, 0, false);
36+
Assert.AreEqual(combination(input.Count, 0), combinations.Count);
37+
38+
input = "pen".ToCharArray().ToList();
39+
combinations = Combination.Find<char>(input, input.Count, false);
40+
Assert.AreEqual(combination(input.Count, input.Count), combinations.Count);
3341
}
3442

3543

@@ -47,6 +55,14 @@ public void Combination_With_Repetitions_Smoke_Test()
4755
input = "scan".ToCharArray().ToList();
4856
combinations = Combination.Find<char>(input, 3, true);
4957
Assert.AreEqual(combination(input.Count + 3 - 1, 3), combinations.Count);
58+
59+
input = "scan".ToCharArray().ToList();
60+
combinations = Combination.Find<char>(input, 0, true);
61+
Assert.AreEqual(combination(input.Count + 0 - 1, 0), combinations.Count);
62+
63+
input = "scan".ToCharArray().ToList();
64+
combinations = Combination.Find<char>(input, input.Count, true);
65+
Assert.AreEqual(combination(input.Count + input.Count - 1, input.Count), combinations.Count);
5066
}
5167

5268
}

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