Array construction - HackerRank university codesprint - score 0, pass only one test case

ArrayConstruction_1.cs

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

namespace ArrayConstruction_P1
{
    class ArrayConstruction
    {
        /*
         * Array construction:
         * 
         * start time: 11:16pm
         * end time: 11:32pm 
         * finish of writing first version
         * Try to score 1<=q <= 10 
         * 10% of 80 - 8 points
         * 
         * submit second time:
         * 12:33pm
         * first time, run-time error on sample test case
         */
        static void Main(string[] args)
        {
            process(); 
            //testCase1(); 
        }

        private static void testCase1()
        {
            string[] arr = "3 3 4".Split(' ');

                int n = Convert.ToInt32(arr[0]);
                int s = Convert.ToInt32(arr[1]);
                int k = Convert.ToInt32(arr[2]);

            Console.WriteLine(lexicoSmallest(n, s, k));
        }

        private static void process()
        {
            int q = Convert.ToInt32(Console.ReadLine());

            for (int i = 0; i < q; i++)
            {
                string[] arr = Console.ReadLine().Split(' ');

                int n = Convert.ToInt32(arr[0]);
                int s = Convert.ToInt32(arr[1]);
                int k = Convert.ToInt32(arr[2]);

                Console.WriteLine(lexicoSmallest(n, s, k));
            }
        }

        /*
         * Nov. 11, 2016
         * start time: 11:21pm 
         * 
         * brute force solution, try to get 
         * 1<= n <=5
         * 0<= s <=10 
         * 0<= k <=20
         */
        private static string lexicoSmallest(int n, int s, int k)
        {
            int[] arr = new int[n];
            IList<string> list = new List<string>();             
            
            StringBuilder sb = new StringBuilder();

            buildResult(list, n, s, k, 0, sb);

            if (list.Count == 0)
                return "-1"; 

            return list[0].ToString(); 
        }

        /*
         * use this code as an example
         * https://github.com/jianminchen/Leetcode_C-/blob/master/17LetterCombinationOfAPhoneNUmber_DFS.cs
         * 
         * Nov. 12, 2016
         * DFS
         * 
         * make the array increasing order
         * 
         * Time complexity: 
         * 
         */
        private static void buildResult(
           IList<string> list, 
           int length, 
           int sum, 
           int sumDiff, 
           int index, 
           StringBuilder current
                )
        {
            if (checkLength(current, length))
            {
                string s = current.ToString();
                if (!sumExactly(current, sum) ||
                   !sumDiffExactly(current, sumDiff))
                    return; 

                keepSmallerOne(list, current);

                return; 
            }

            int sumArr = calSum(current); 

            int min = getLastOne(current); 
            for(int i = min; i<= sum; i++)
            {
                bool isReady = sumChecking(sum, sumArr, i) &&
                   sumDiffChecking(sumDiff, current, i);

                if (!isReady)
                    break;

                string add = (current.ToString().Length==0 )?i.ToString() : (" " + i.ToString());
                current.Append(add);
                buildResult(list, length, sum, sumDiff, index +1, current);

                int len = add.Length; 
                current.Remove(current.Length - len, len);  // remove last char
            }
        }

        /*
         * start: 12:40pm
         * 
         */
        private static bool sumExactly(StringBuilder sb, int sum)
        {
            int sumArr = calSum(sb);

            return (sumArr == sum); 
        }

        /*
         * start: 12:44pm 
         * end time: 12:50pm 
         */
        private static bool sumDiffExactly(StringBuilder sb, int sumDiff)
        {
            string s = sb.ToString();

            if (s == null || s.Length == 0)
                return false;

            int[] arr = toIntArr(s);

            int count = 0;   
            for(int i=0; i< arr.Length; i++)
                for(int j=i+1; j< arr.Length; j++)
                {
                    count += Math.Abs(arr[i] - arr[j]); 
                }

            return count == sumDiff; 
        }

        /*
         * Fix the bug - check length of array
         * start: 12:32pm 
        */
        private static bool checkLength(StringBuilder sb, int length)
        {
            string s = sb.ToString();
            if (s == null || s.Length == 0)
                return false;
            return s.Split(' ').Length >= length; 
        }

        /*
         * start: 10:00am
         */
        private static int calSum(StringBuilder current)
        {
            string s = current.ToString();
            if (s == null || s.Length == 0)
                return 0;

            //int[] arr = Array.ConvertAll(s.Split(' '), int.Parse);
            int[] arr = toIntArr(s); 
            return arr.Sum(); 
        }

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

            string[] arr = s.Split(' ');

            int[] res = new int[arr.Length]; 
            for(int i = 0; i < arr.Length; i++)
            {
                res[i] = Convert.ToInt32(arr[i]); 
            }

            return res; 
        }

        /*
         * Nov. 12, 2016
         * start time: 10:46am
         * http://stackoverflow.com/questions/4387901/how-to-convert-a-string-to-int-in-c-sharp-and-net-2-0
         */
        private static bool sumCheckingRetired(
            int             sum, 
            StringBuilder   current, 
            int             newItem)
        {
           // int[] arr = Array.ConvertAll(current.ToString().Split(' '), int.Parse);
            int[] arr = toIntArr(current.ToString()); 

            if (newItem + arr.Sum() < sum)
                return true;
            else
                return false; 
        }

        private static bool sumChecking(
            int sum,
            int sumArray,
            int newItem)
        {
            if (newItem + sumArray <= sum)
                return true;
            else
                return false;
        }

        /*
         * start: 11:05am
         */
        private static int getLastOne(StringBuilder sb)
        {
            string s = sb.ToString();
            if (s == null || s.Length == 0)
                return 0; 

            string[] arr = sb.ToString().Split(' ');

            return (Convert.ToInt32(arr[arr.Length - 1])); 
        }

        /*
         * start: 11:07am
         */
        private static bool sumDiffChecking(
            int sum, 
            StringBuilder current, 
            int newItem
            )
        {
            string s = current.ToString();

            if (s == null || s.Length == 0)
                return true; 

            //int[] arr = Array.ConvertAll(current.ToString().Split(' '), int.Parse);
            int[] arr = toIntArr(current.ToString()); 

            int len = arr.Length;

            int total = 0; 
            for(int i=0; i<= len; i++)
                for(int j=i+1; j<=len; j++)
                {
                    int first  = (i == len) ? newItem : arr[i];
                    int second = (j == len) ? newItem : arr[j];

                    total += Math.Abs(first - second); 
                }

            if (total <= sum)
                return true;
            else
                return false; 
        }

        /*
         * start: 11:21am 
         */
        private static void  keepSmallerOne(
            IList<string> list, 
            StringBuilder current)
        {
            if (list.Count == 0)
            {
                list.Add(current.ToString());
                return; 
            }

            string prev = list[0].ToString();

           // int[] arr1 = Array.ConvertAll(prev.Split(' '), int.Parse);
           // int[] arr2 = Array.ConvertAll(current.ToString().Split(' '), int.Parse); 

            int[] arr1 = toIntArr(prev);
            int[] arr2 = toIntArr(current.ToString()); 

            bool firstOneSmaller = true; 
            for(int i = 0; i < arr1.Length; i++)
            {
                if(arr1[i] > arr2[i])
                {
                    firstOneSmaller = false;
                    break; 
                }
            }

            if(!firstOneSmaller)
            {
                list.Clear();
                list.Add(current.ToString()); 
            }

            return; 
        }
    }
}