How to Exclude Two Ilist<int[]>

Deer Park

I have a program where I first get the List of Integer array by calling a method whose return type is IEnumerable
var result = Myclass.GetNumbers(someInputVal);

say - result contains [0] - {1,2,3}
[1]- {4,5,6}

public static IEnumerable GetNumbers (int someInputval)
{
List result = new List();

// Number processing done here
return result;
}
And I have another List of int[], say result1

List<int[]> result1 = new List<int[]> {
                new int[]{1,2,3}
                ,new int[]{7,8,9}
            };

Now, How do I compare result with result1 and exclude the value which are common between result and result1 from result

So, the result list should have only {{4,5,6} .

I am not sure how will I be able to achieve this efficiently. I will have many InputSet's that I will need to check in the "result".
Appreciate your help.

2 Replies

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Vulpes14y ago
Accepted answer
I'd use an IEqualityComparer to compare the arrays and LINQ's Except() extension method to get the 'set difference' between the two. The code will be something like the following.

I've assumed that the order of the integer array is significant i.e. for two arrays to be considered equal, their corresponding elements should be equal:

using System;
using System.Collections.Generic;
using System.Linq;

class Int32ArrayEqualityComparer : IEqualityComparer
{
public bool Equals(int[] ia1, int[] ia2)
{
if (ia1 == null || ia2 == null) return false;
if (ia1.Length != ia2.Length) return false;

for(int i = 0; i < ia1.Length; i++)
{
if (ia1[i] != ia2[i]) return false;
}
return true;
}

public int GetHashCode(int[] ia)
{
if (ia == null || ia.Length == 0) return 0;
int combined = ia[0];
for(int i = 1; i < ia.Length; i++) combined ^= ia[i];
return combined.GetHashCode();
}
}

class Test
{
static void Main()
{
List result = new List {new int[]{1,2,3}, new int[]{4,5,6} };
List result1 = new List {new int[]{1,2,3}, new int[]{7,8,9} };
List result2 = result.Except(result1, new Int32ArrayEqualityComparer()).ToList();

// check it worked
foreach(int[] ia in result2)
{
foreach(int i in ia) Console.Write("{0} ", i);
Console.WriteLine();
}

Console.ReadKey();
}
}
Deer Park13y ago
This is correct when the order of the integer array is not relevant.