Reverse Shuffle Merge - still only one case pass - after 2 hours working

ReverseShuffleMerge2.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ReverseMergeString
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(reverseMerge(Console.ReadLine())); 
        }

        /*
         * Failed test case:
         * bdabaceadaedaaaeaecdeadababdbeaeeacacaba
         * output:
         * aaaaaabaaceededecbdb
         * Julia's output "cdeadababdbeaeeacacaba"	string

         */
        public static string reverseMerge(string s)
        {
            if (!canBeReverseMerged(s))
                return "";

            int len = s.Length;
            int half = len / 2;                       

            int[] A = getCountArray(s);
            int[] skipLog = getHalf(A);

            String output = ""; 
            for (int i = 0; i < s.Length; i++ )
            {
                char c = s[i];
                if (firstOneNonzero(skipLog, c) || !greedyCheckBackwardSkip(skipLog, c))                
                    output += c;                                    
                else
                {
                    if (!canDecrement(skipLog, c))
                        return ""; // something is wrong 
                }
            }

            return output; 
        }

        private static bool canDecrement(int[] A, char c)
        {
            A[c-'a']--;
            return (A[c - 'a'] >= 0); 
        }


        /*
         * if c can be added to the output 
         */
        private static bool greedyCheckForward(int[] A, char c)
        {           
            for(int i=0; i<'c'-'a';i++)
            {
                if (A[i] > 0)
                    return false; 
            }

            return true; 
        }

        /*
         * Skip rules - only two :
         * 1. First, if there is one to skip before the input char 
         * 2. Second, if the char is the first one in the list, alway go to true
         */
        private static bool greedyCheckBackwardSkip(int[] A, char c)
        {
            for (int i = 25; i > 'c' - 'a'; i--) // bug: index problem - why I am still need debugger here!!!
            {
                if (A[i] > 0 && A[i] != (c - 'a'))                                  
                        return true;                
            }

            return false;
        }

        // c is first char nonzeor 
        private static bool firstOneNonzero(int[] A, char c)
        {
            for (int i = 25; i > 'c' - 'a'; i--) // bug: index problem - why I am still need debugger here!!!
            {
                if (A[i] > 0 )
                    return false;
            }

            return true;
        }

        private static int[] getHalf(int[] A)
        {
            int[] ret = new int[26]; 

            for(int i=0; i<26; i++)
            {
                ret[i] = A[i] / 2; 
            }

            return ret; 
        }

        private static bool isHalf(int[] B, int[] A)
        {
            for(int i=0;i<26;i++)
            {
                if (B[i] * 2 == A[i])
                    continue;
                else
                    return false; 
            }

            return true; 
        }

        // assume both string have same length 
        // because it is reverse string
        private static string smallOne(string tmpS1, string tmpS2)
        {
            string s1 = reverse(tmpS1);
            string s2 = reverse(tmpS2); 

            int len = s1.Length; 

            for(int i=0;i<len;i++)
            {
                if (s1[i] < s2[i])
                    return tmpS1;
                else if (s1[i] > s2[i])
                    return tmpS2; 
            }
            // both are the same, any one
            return tmpS1; 
        }

        private static string reverse(string s)
        {
            StringBuilder newS = new StringBuilder();

            for (int i = s.Length - 1; i >= 0; i--)
                newS.Append(s[i].ToString());

            return newS.ToString(); 
        }

        private static bool canBeReverseMerged(string s)
        {
            if (s == null || s.Length == 0) return true;

            int[] A = new int[26]; 
            for(int i=0; i < s.Length;i++)
            {
                A[s[i]-'a']++; 
            }
             
            for(int i=0;i<26;i++)
            {
                if (A[i] % 2 == 1)
                    return false; 
            }

            return true; 
        }

        private static int[] getCountArray(string s)
        {           
            int[] A = new int[26];
            if (s == null || s.Length == 0) return A;

            for (int i = 0; i < s.Length; i++)
            {
                A[s[i] - 'a']++;
            }

            return A;             
        }
    }
}