HashSet<T>.Overlaps(IEnumerable<T>) Method

Definition

Namespace:

System.Collections.Generic

Assembly:

System.Collections.dll

Source:

HashSet.cs

Determines whether the current HashSet<T> object and a specified collection share common elements.

public:
 virtual bool Overlaps(System::Collections::Generic::IEnumerable<T> ^ other);

public bool Overlaps (System.Collections.Generic.IEnumerable<T> other);

abstract member Overlaps : seq<'T> -> bool
override this.Overlaps : seq<'T> -> bool

Public Function Overlaps (other As IEnumerable(Of T)) As Boolean

Parameters

other

IEnumerable<T>

The collection to compare to the current HashSet<T> object.

Returns

Boolean

true if the HashSet<T> object and other share at least one common element; otherwise, false.

Implements

Overlaps(IEnumerable<T>) Overlaps(IEnumerable<T>)

Exceptions

ArgumentNullException

other is null.

Examples

The following example creates two disparate HashSet<T> objects and compares them to each another. In this example, allNumbers and lowNumbers are shown to share common elements using the Overlaps method.

HashSet<int> lowNumbers = new HashSet<int>();
HashSet<int> allNumbers = new HashSet<int>();

for (int i = 1; i < 5; i++)
{
    lowNumbers.Add(i);
}

for (int i = 0; i < 10; i++)
{
    allNumbers.Add(i);
}

Console.Write("lowNumbers contains {0} elements: ", lowNumbers.Count);
DisplaySet(lowNumbers);

Console.Write("allNumbers contains {0} elements: ", allNumbers.Count);
DisplaySet(allNumbers);

Console.WriteLine("lowNumbers overlaps allNumbers: {0}",
    lowNumbers.Overlaps(allNumbers));

Console.WriteLine("allNumbers and lowNumbers are equal sets: {0}",
    allNumbers.SetEquals(lowNumbers));

// Show the results of sub/superset testing
Console.WriteLine("lowNumbers is a subset of allNumbers: {0}",
    lowNumbers.IsSubsetOf(allNumbers));
Console.WriteLine("allNumbers is a superset of lowNumbers: {0}",
    allNumbers.IsSupersetOf(lowNumbers));
Console.WriteLine("lowNumbers is a proper subset of allNumbers: {0}",
    lowNumbers.IsProperSubsetOf(allNumbers));
Console.WriteLine("allNumbers is a proper superset of lowNumbers: {0}",
    allNumbers.IsProperSupersetOf(lowNumbers));

// Modify allNumbers to remove numbers that are not in lowNumbers.
allNumbers.IntersectWith(lowNumbers);
Console.Write("allNumbers contains {0} elements: ", allNumbers.Count);
DisplaySet(allNumbers);

Console.WriteLine("allNumbers and lowNumbers are equal sets: {0}",
    allNumbers.SetEquals(lowNumbers));

// Show the results of sub/superset testing with the modified set.
Console.WriteLine("lowNumbers is a subset of allNumbers: {0}",
    lowNumbers.IsSubsetOf(allNumbers));
Console.WriteLine("allNumbers is a superset of lowNumbers: {0}",
    allNumbers.IsSupersetOf(lowNumbers));
Console.WriteLine("lowNumbers is a proper subset of allNumbers: {0}",
    lowNumbers.IsProperSubsetOf(allNumbers));
Console.WriteLine("allNumbers is a proper superset of lowNumbers: {0}",
    allNumbers.IsProperSupersetOf(lowNumbers));

void DisplaySet(HashSet<int> set)
{
    Console.Write("{");
    foreach (int i in set)
    {
        Console.Write(" {0}", i);
    }
    Console.WriteLine(" }");
}

/* This code example produces output similar to the following:
* lowNumbers contains 4 elements: { 1 2 3 4 }
* allNumbers contains 10 elements: { 0 1 2 3 4 5 6 7 8 9 }
* lowNumbers overlaps allNumbers: True
* allNumbers and lowNumbers are equal sets: False
* lowNumbers is a subset of allNumbers: True
* allNumbers is a superset of lowNumbers: True
* lowNumbers is a proper subset of allNumbers: True
* allNumbers is a proper superset of lowNumbers: True
* allNumbers contains 4 elements: { 1 2 3 4 }
* allNumbers and lowNumbers are equal sets: True
* lowNumbers is a subset of allNumbers: True
* allNumbers is a superset of lowNumbers: True
* lowNumbers is a proper subset of allNumbers: False
* allNumbers is a proper superset of lowNumbers: False
*/

let displaySet (set: HashSet<int>) =
    printf "{"

    for i in set do
        printf $" {i}"

    printfn " }"

let lowNumbers = HashSet<int>()
let allNumbers = HashSet<int>()

for i = 1 to 4 do
    lowNumbers.Add i |> ignore


for i = 0 to 9 do
    allNumbers.Add i |> ignore

printf $"lowNumbers contains {lowNumbers.Count} elements: "
displaySet lowNumbers

printf $"allNumbers contains {allNumbers.Count} elements: "
displaySet allNumbers

printfn $"lowNumbers overlaps allNumbers: {lowNumbers.Overlaps allNumbers}"

printfn $"allNumbers and lowNumbers are equal sets: {allNumbers.SetEquals lowNumbers}"

// Show the results of sub/superset testing
printfn $"lowNumbers is a subset of allNumbers: {lowNumbers.IsSubsetOf allNumbers}"
printfn $"allNumbers is a superset of lowNumbers: {allNumbers.IsSupersetOf lowNumbers}"
printfn $"lowNumbers is a proper subset of allNumbers: {lowNumbers.IsProperSubsetOf allNumbers}"
printfn $"allNumbers is a proper superset of lowNumbers: {allNumbers.IsProperSupersetOf lowNumbers}"

// Modify allNumbers to remove numbers that are not in lowNumbers.
allNumbers.IntersectWith lowNumbers
printf $"allNumbers contains {allNumbers.Count} elements: "
displaySet allNumbers

printfn $"allNumbers and lowNumbers are equal sets: {allNumbers.SetEquals lowNumbers}"

// Show the results of sub/superset testing with the modified set.
printfn $"lowNumbers is a subset of allNumbers: {lowNumbers.IsSubsetOf allNumbers}"
printfn $"allNumbers is a superset of lowNumbers: {allNumbers.IsSupersetOf lowNumbers}"
printfn $"lowNumbers is a proper subset of allNumbers: {lowNumbers.IsProperSubsetOf allNumbers}"
printfn $"allNumbers is a proper superset of lowNumbers: {allNumbers.IsProperSupersetOf lowNumbers}"
// This code example produces output similar to the following:
//     lowNumbers contains 4 elements: { 1 2 3 4 }
//     allNumbers contains 10 elements: { 0 1 2 3 4 5 6 7 8 9 }
//     lowNumbers overlaps allNumbers: True
//     allNumbers and lowNumbers are equal sets: False
//     lowNumbers is a subset of allNumbers: True
//     allNumbers is a superset of lowNumbers: True
//     lowNumbers is a proper subset of allNumbers: True
//     allNumbers is a proper superset of lowNumbers: True
//     allNumbers contains 4 elements: { 1 2 3 4 }
//     allNumbers and lowNumbers are equal sets: True
//     lowNumbers is a subset of allNumbers: True
//     allNumbers is a superset of lowNumbers: True
//     lowNumbers is a proper subset of allNumbers: False
//     allNumbers is a proper superset of lowNumbers: False

Shared Sub Main()

    Dim lowNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()
    Dim allNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()

    For i As Integer = 1 To 4
        lowNumbers.Add(i)
    Next i

    For i As Integer = 0 To 9
        allNumbers.Add(i)
    Next i


    Console.Write("lowNumbers contains {0} elements: ", lowNumbers.Count)
    DisplaySet(lowNumbers)

    Console.Write("allNumbers contains {0} elements: ", allNumbers.Count)
    DisplaySet(allNumbers)

    Console.WriteLine("lowNumbers overlaps allNumbers: {0}", _
        lowNumbers.Overlaps(allNumbers))

    Console.WriteLine("allNumbers and lowNumbers are equal sets: {0}", _
        allNumbers.SetEquals(lowNumbers))

    ' Show the results of sub/superset testing
    Console.WriteLine("lowNumbers is a subset of allNumbers: {0}", _
        lowNumbers.IsSubsetOf(allNumbers))
    Console.WriteLine("allNumbers is a superset of lowNumbers: {0}", _
        allNumbers.IsSupersetOf(lowNumbers))
    Console.WriteLine("lowNumbers is a proper subset of allNumbers: {0}", _
        lowNumbers.IsProperSubsetOf(allNumbers))
    Console.WriteLine("allNumbers is a proper superset of lowNumbers: {0}", _
        allNumbers.IsProperSupersetOf(lowNumbers))

    ' Modify allNumbers to remove numbers that are not in lowNumbers.
    allNumbers.IntersectWith(lowNumbers)
    Console.Write("allNumbers contains {0} elements: ", allNumbers.Count)
    DisplaySet(allNumbers)

    Console.WriteLine("allNumbers and lowNumbers are equal sets: {0}", _
        allNumbers.SetEquals(lowNumbers))

    ' Show the results of sub/superset testing with the modified set.
    Console.WriteLine("lowNumbers is a subset of allNumbers: {0}", _
        lowNumbers.IsSubsetOf(allNumbers))
    Console.WriteLine("allNumbers is a superset of lowNumbers: {0}", _
        allNumbers.IsSupersetOf(lowNumbers))
    Console.WriteLine("lowNumbers is a proper subset of allNumbers: {0}", _
        lowNumbers.IsProperSubsetOf(allNumbers))
    Console.WriteLine("allNumbers is a proper superset of lowNumbers: {0}", _
        allNumbers.IsProperSupersetOf(lowNumbers))
End Sub
' This code example produces output similar to the following:
' lowNumbers contains 4 elements: { 1 2 3 4 }
' allNumbers contains 10 elements: { 0 1 2 3 4 5 6 7 8 9 }
' lowNumbers overlaps allNumbers: True
' allNumbers and lowNumbers are equal sets: False
' lowNumbers is a subset of allNumbers: True
' allNumbers is a superset of lowNumbers: True
' lowNumbers is a proper subset of allNumbers: True
' allNumbers is a proper superset of lowNumbers: True
' allNumbers contains 4 elements: { 1 2 3 4 }
' allNumbers and lowNumbers are equal sets: True
' lowNumbers is a subset of allNumbers: True
' allNumbers is a superset of lowNumbers: True
' lowNumbers is a proper subset of allNumbers: False
' allNumbers is a proper superset of lowNumbers: False

Remarks

This method is an O(n) operation, where n is the number of elements in other.