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Ingy döt Net 2023-07-01 11:58:00 -04:00
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Task/Set-consolidation/C-sharp/set-consolidation.cs Normal file
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using System;
using System.Linq;
using System.Collections.Generic;
public class SetConsolidation
{
public static void Main()
{
var setCollection1 = new[] {new[] {"A", "B"}, new[] {"C", "D"}};
var setCollection2 = new[] {new[] {"A", "B"}, new[] {"B", "D"}};
var setCollection3 = new[] {new[] {"A", "B"}, new[] {"C", "D"}, new[] {"B", "D"}};
var setCollection4 = new[] {new[] {"H", "I", "K"}, new[] {"A", "B"}, new[] {"C", "D"},
new[] {"D", "B"}, new[] {"F", "G", "H"}};
var input = new[] {setCollection1, setCollection2, setCollection3, setCollection4};
foreach (var sets in input) {
Console.WriteLine("Start sets:");
Console.WriteLine(string.Join(", ", sets.Select(s => "{" + string.Join(", ", s) + "}")));
Console.WriteLine("Sets consolidated using Nodes:");
Console.WriteLine(string.Join(", ", ConsolidateSets1(sets).Select(s => "{" + string.Join(", ", s) + "}")));
Console.WriteLine("Sets consolidated using Set operations:");
Console.WriteLine(string.Join(", ", ConsolidateSets2(sets).Select(s => "{" + string.Join(", ", s) + "}")));
Console.WriteLine();
}
}
/// <summary>
/// Consolidates sets using a connected-component-finding-algorithm involving Nodes with parent pointers.
/// The more efficient solution, but more elaborate code.
/// </summary>
private static IEnumerable<IEnumerable<T>> ConsolidateSets1<T>(IEnumerable<IEnumerable<T>> sets,
IEqualityComparer<T> comparer = null)
{
if (comparer == null) comparer = EqualityComparer<T>.Default;
var elements = new Dictionary<T, Node<T>>();
foreach (var set in sets) {
Node<T> top = null;
foreach (T value in set) {
Node<T> element;
if (elements.TryGetValue(value, out element)) {
if (top != null) {
var newTop = element.FindTop();
top.Parent = newTop;
element.Parent = newTop;
top = newTop;
} else {
top = element.FindTop();
}
} else {
elements.Add(value, element = new Node<T>(value));
if (top == null) top = element;
else element.Parent = top;
}
}
}
foreach (var g in elements.Values.GroupBy(element => element.FindTop().Value))
yield return g.Select(e => e.Value);
}
private class Node<T>
{
public Node(T value, Node<T> parent = null) {
Value = value;
Parent = parent ?? this;
}
public T Value { get; }
public Node<T> Parent { get; set; }
public Node<T> FindTop() {
var top = this;
while (top != top.Parent) top = top.Parent;
//Set all parents to the top element to prevent repeated iteration in the future
var element = this;
while (element.Parent != top) {
var parent = element.Parent;
element.Parent = top;
element = parent;
}
return top;
}
}
/// <summary>
/// Consolidates sets using operations on the HashSet&lt;T&gt; class.
/// Less efficient than the other method, but easier to write.
/// </summary>
private static IEnumerable<IEnumerable<T>> ConsolidateSets2<T>(IEnumerable<IEnumerable<T>> sets,
IEqualityComparer<T> comparer = null)
{
if (comparer == null) comparer = EqualityComparer<T>.Default;
var currentSets = sets.Select(s => new HashSet<T>(s)).ToList();
int previousSize;
do {
previousSize = currentSets.Count;
for (int i = 0; i < currentSets.Count - 1; i++) {
for (int j = currentSets.Count - 1; j > i; j--) {
if (currentSets[i].Overlaps(currentSets[j])) {
currentSets[i].UnionWith(currentSets[j]);
currentSets.RemoveAt(j);
}
}
}
} while (previousSize > currentSets.Count);
foreach (var set in currentSets) yield return set.Select(value => value);
}
}