Question

I have the following objects defined:

public class MyGroup
{
    public MyItem[] Items;
}

public class MyItem
{
    public int Val;
}

Say I have a list as List where each MyGroup object contains a varying number of MyItems; which in turn contains a varying value for Val.

How can I find the subset of MyGroup objects that contains the lowest Val across all MyGroup objects.

E.g:
If I define the list with following values

• MyGroup1 contains a MyItem for each of the following values: 1, 5 and
  7
• MyGroup2 contains a MyItem for each of the following values: 3 and,
  8
• MyGroup3 contains a MyItem for each of the following values: 2, 4,
  5 and, 7

Then the returned value will be MyGroup1 (as a single item list) because it contains the value 1 which is the lowest across all values.

However, if there are multiple values with the lowest value like:

• MyGroup1 contains a MyItem for each of the following values: 1, 5 and 7
• MyGroup2 contains a MyItem for each of the following values: 3 and, 8
• MyGroup3 contains a MyItem for each of the following values: 1, 4, 5 and, 7

Then it will return MyGroup1 and MyGroup3 in a list.

Thanks in advance.

Answer 1

int lowestValue = groups.SelectMany(group => group.Items)
                  .Min(item => item.Val);

IEnumerable<MyGroup> result = groups.Where(group => 
    group.Items.Select(item => item.Val).Contains(lowestValue));

This will be a two pass algorithm. If you were suitably motivated you could do it in a single pass by keeping track of all of the items containing the min value while searching for that min value.