Keep scanning through the array and calculating the maximum sub-array that ends at every position. The sub-array will either contain a range of numbers if the array has intermixed positive and negative values, or it will contain the least negative value if the array has only negative values.

Use Kadane’s algorithm which runs in O(n) time.

class Program { static void Main(string[] args) { int[] arr = new int[] { 5, -2, 3, 18, -4, 29, 2, -5 }; FindMaximumSumofAllSubArrays(arr); Console.ReadLine(); } private static void FindMaximumSumofAllSubArrays(int[] arr) { List<int> arrList = new List<int>(); int maxSumSoFar = -2147483648; int curSum = 0; //loop for for chcking if all numbers in an array are negative. foreach (int item in arr) { if (maxSumSoFar < item) { maxSumSoFar = item; } } if (maxSumSoFar < 0) { Console.WriteLine("All Array Numbers are Negative and Maximum sum is " + maxSumSoFar); return; } maxSumSoFar = 0; foreach (int item in arr) { curSum += item; if (curSum > maxSumSoFar) { maxSumSoFar = curSum; } if (curSum < 0) { curSum = 0; } } Console.WriteLine(maxSumSoFar); } }