leetcode830

public class Solution
    {
        public IList<IList<int>> LargeGroupPositions(string S)
        {
            //"babaaaabbb"
            var list = new List<IList<int>>();
            int len = S.Length;
            if (len > 0)
            {
                var last = S[0];
                var begin = 0;
                var end = S.Length - 1;

                for (int i = 0; i < len; i++)
                {
                    var cur = S[i];
                    if (last != cur)
                    {
                        end = i - 1;
                        var dif = end - begin + 1;
                        if (dif >= 3)
                        {
                            var poslist = new List<int>();
                            poslist.Add(begin);
                            poslist.Add(end);
                            list.Add(poslist);
                        }
                        last = S[i];
                        begin = i;
                    }
                    end = i;
                }

                if (end - begin >= 2)
                {
                    var list3 = new List<int>();
                    list3.Add(begin);
                    list3.Add(end);
                    list.Add(list3);
                }
            }

            return list;
        }
    }