Question

I need to get a Kvp from a list of List<KeyValuePair<Int, Int>> depending on the minimum value.

I have tried this:

KeyValuePair<Int, Int> kvp= listOfKvps.Min(e=> e.Key);

but this return only the value, not the whole KeyValuePair which I need.

Answer 1

There is no inbuilt MinBy method, so you could either write a MinBy extension method, or just .OrderBy(x => x.Key).First(). A MinBy would be O(n) so would be more efficient – but more code to write ;p

For example, you could use:

var kvp= listOfKvps.MinBy(e=> e.Key);

with:

public static class SomeUtil {
    public static TSource MinBy<TSource, TValue>(
        this IEnumerable<TSource> source, Func<TSource, TValue> selector) {
        using (var iter = source.GetEnumerator())
        {
            if (!iter.MoveNext()) throw new InvalidOperationException("no data");
            var comparer = Comparer<TValue>.Default;
            var minItem = iter.Current;
            var minValue = selector(minItem);
            while (iter.MoveNext())
            {
                var item = iter.Current;
                var value = selector(item);
                if (comparer.Compare(minValue, value) > 0)
                {
                    minItem = item;
                    minValue = value;
                }
            }
            return minItem;
        }
    }   
}