Max contiguous subarray sum

So, i just had an online programming assessment where i was given 2 problems one of which was this contiguous subarray sum provided 2 Complex coding questions + 8 mcqs and was to be completed in 1 hr.

Here i would be discussing one of the above mentioned max contiguous sum of subarray. Usually the tough part i find was handling negative numbers and contiguously. What i did was i first applied a Collection.sort(arr) to the given array and i again sorted the negative values by their absolute value like for i.. arr.get(i)! =abs(arr.get(i)) for j.. if arr.get(i)>arr.get(j) then swap so final array is -1, -2, 3,4,5 for example for given random numbers array and i mantain a max after each i and all j iterations per that I have if max<sum(i.e. sum+arr.get(allj)+arr(particular i) then max=sum. So this was giving me the max sum but I got 4 cases passed out of 14 and i thought the reason being sorted array wouldnt be always contiguous so any suggestions so as to how would i inculcate such contiguous logic within this to make it work for all cases.

I think you mistook contiguous subarray problem to a subset problem instead cause you shouldn't be using sorting in the logic. You could refer the question here which handles negative numbers as well. https://www.geeksforgeeks.org/largest-sum-contiguous-subarray/

There is an excellent explanation of the Maximum Subarray Problem on this page of Wikipedia. Essentially, you are looking for an implementation of Kadane's algorithm, which is explained in the article.