Question

I need help with an algorithm that will add an index to the duplicate elements in a string list in C#.

i.e.

A, B, C, D, A, B, E, F, A

will become

A, B, C, D, A (1), B (1), E, F, A (2)

Answer 1

var strings = new string[] { "A", "B", "C", "D", "A", "B", "E", "F", "A" };

Dictionary<string, int> counts = new Dictionary<string, int>();
for (int i = 0; i < strings.Length; ++i)
{
    if (counts.ContainsKey(strings[i]))
        strings[i] = string.Format("{0} ({1})", strings[i], counts[strings[i]]++);
    else
        counts.Add(strings[i], 1);
}