More efficient way to get all indexes of a character in a string

Question

Instead of looping through each character to see if it\'s the one you want then adding the index your on to a list like so:

     var foundIndexes = new List&         


        

Answer 1

You can use String.IndexOf, see example below:

    string s = "abcabcabcabcabc";
    var foundIndexes = new List();

    long t1 = DateTime.Now.Ticks;
    for (int i = s.IndexOf('a'); i > -1; i = s.IndexOf('a', i + 1))
        {
         // for loop end when i=-1 ('a' not found)
                foundIndexes.Add(i);
        }
    long t2 = DateTime.Now.Ticks - t1; // read this value to see the run time