search List for string .StartsWith()

Question

I have a

List

with 1500 strings. I am now using the following code to pull out only string that start with the string prefix

Answer 1

So many approches were analyzed to achive minimum data capacity and high performance. The first place is: all prefixes are stored in dictionary: key - prefix, values - items appropriate for prefix.

Here simple implementation of this algorithm:

public class Trie
{
    #region Constructors

    public Trie(
        IEnumerable items,
        Func keySelector,
        IComparer comparer)
    {
        this.KeySelector = keySelector;
        this.Comparer = comparer;
        this.Items = (from item in items
                      from i in Enumerable.Range(1, this.KeySelector(item).Length)
                      let key = this.KeySelector(item).Substring(0, i)
                      group item by key)
                     .ToDictionary( group => group.Key, group => group.ToList());
    }

    #endregion

    #region Properties

    protected Dictionary> Items { get; set; }

    protected Func KeySelector { get; set; }

    protected IComparer Comparer { get; set; }

    #endregion

    #region Methods

    public List Retrieve(string prefix)
    {
        return  this.Items.ContainsKey(prefix)
            ? this.Items[prefix]
            : new List();
    }

    public void Add(TItem item)
    {
        var keys = (from i in Enumerable.Range(1, this.KeySelector(item).Length)
                    let key = this.KeySelector(item).Substring(0, i)
                    select key).ToList();
        keys.ForEach(key =>
        {
            if (!this.Items.ContainsKey(key))
            {
                this.Items.Add(key, new List { item });
            }
            else if (this.Items[key].All(x => this.Comparer.Compare(x, item) != 0))
            {
                this.Items[key].Add(item);
            }
        });
    }

    public void Remove(TItem item)
    {
        this.Items.Keys.ToList().ForEach(key =>
        {
            if (this.Items[key].Any(x => this.Comparer.Compare(x, item) == 0))
            {
                this.Items[key].RemoveAll(x => this.Comparer.Compare(x, item) == 0);
                if (this.Items[key].Count == 0)
                {
                    this.Items.Remove(key);
                }
            }
        });
    }

    #endregion
}