Find highest integer in a Generic List using C#?

Question

I have the following List<int> collection and I need to find the highest integer in the collection. It could have an arbitrary number of integers and I can have same integer value for multiple times.

List<int> MyList = new List<int> { 3, 4, 6, 7, 9, 3, 4, 5, 5 };

What is the best algorithm to use for finding the highest integer? I am using C# and the .NET 3.5 framework.

Answer 1

You can just do:

int max = MyList.Max();

See Enumerable.Max for details.

Answer 2

Enumerable has a Max function that will do this.

Looking at the implementation for the integer specific method using Reflector, the method loops through each element in the the IEnumerable source and compares it with what was previously the highest value.

Answer 3

If you need to retrieve the maximum value frequently you might think about creating your own list class (or derive from List) which keeps the maximum item in a cache. Such a class could look like this:

public class MaxList<T> : IList<T>, ICollection<T>, IEnumerable<T>
{
    T Maximum { get; set; }
    List<T> _list;

    public T this[int index] { get; set; }

    public void Add(T item)
    {
        if (item > this.Maximum)
        {
            this.Maximum = item;
        }
        _list.Add(item);
    }

    // ... IEnumerable<T>, ICollection<T> and IList<T> members 

}

Alternatively, you could derive from List directly and overwrite the Add and Remove methods (basically all methods modifying list items) and update the cache accordingly.

If such an approach is really a benefit depends on your scenario. IT definitely is if you have a very large list with is rarely updated and you need to retrieve the maximum frequently. Otherwise go for the solutions already suggested because they are much simpler.

Answer 4

genericlist.Remove(genericlist.Max)