Leetcode 53 divide and conquer

Leetcode53divideandconquer.cs

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

namespace Leetcode53_Maximum_subarray_divide_and_conquer
{
    class Program
    {
        static void Main(string[] args)
        {
        }

        public int MaxSubArray(int[] nums)
        {
            if (nums == null)
                return 0;

            int max = int.MinValue; 

            var result =  maxStartAndMaxEnd(nums, 0, nums.Length - 1, ref max);
            return max; 
        }

        /// <summary>
        /// August 27, 2018
        /// </summary>
        /// <param name="nums"></param>
        /// <param name="start"></param>
        /// <param name="end"></param>
        /// <param name="maxValue"></param>
        /// <returns></returns>
        public static int[] maxStartAndMaxEnd(int[] nums, int start, int end, ref int max)
        { 
            if (start == end)
                return new int[]{nums[start], nums[end]};

            var middle = start + (end - start) / 2;

            if (end - start == 1)
            {
                var number0 = nums[start];
                var number1 = nums[end];
                var twoSum = number0 + number1;

                var maxStart = Math.Max(number0, twoSum);
                var maxEnd = Math.Max(number1, twoSum);
                max = Math.Max(max, twoSum);
                return new int[] { maxStart, maxEnd};
            }

            var sum = 0; 
            if (middle - 1 >= start)
            {
                var leftMax = maxStartAndMaxEnd(nums, start, middle - 1, ref max);
                sum = leftMax[1];
            }

            if (middle <= end)
            {
                var rightMax = maxStartAndMaxEnd(nums, middle, end, ref max);
                sum += rightMax[0];
            }

            // let us consider the range include middle - 1, middle
            max = Math.Max(max, sum);            
            return 
        }
    }
}