Merge multiple lists with variable length “popping” elements from each

Question

I\'d like to sort multiple lists (variable number of them) into single list, but keeping the specific order. For example:

List A: { 1,2,3,4,5 }
List B: { 6,7         


        

Answer 1

For your problem I create static method, which can merge any collections as you want:

public static class CollectionsHandling
{
    /// 

    /// Merge collections to one by index
    /// 
    /// Type of collection elements
    /// Merging Collections
    /// New collection {firsts items, second items...}
    public static IEnumerable Merge(params IEnumerable[] collections)
    {
        // Max length of sent collections
        var maxLength = 0;

        // Enumerators of all collections
        var enumerators = new List>();

        foreach (var item in collections)
        {
            maxLength = Math.Max(item.Count(), maxLength);
            if(collections.Any())
                enumerators.Add(item.GetEnumerator());
        }
        // Set enumerators to first item
        enumerators.ForEach(e => e.MoveNext());

        var result = new List();
        for (int i = 0; i < maxLength; i++)
        {
            // Add elements to result collection
            enumerators.ForEach(e => result.Add(e.Current));

            // Remobve enumerators, in which no longer have elements
            enumerators = enumerators.Where(e => e.MoveNext()).ToList();
        }

        return result;
    }
}

Example of using:

static void Main(string[] args)
{
    var a = new List { 1, 2, 3, 4, 5 };
    var b = new List { 6, 7, 8 };
    var c = new List { 9, 10, 11, 12 };

    var result= CollectionsHandling.Merge(a, b, c);
}

When you understand how it works, it will be possible to reduce the method of smaller.