Improve the following function so the time complexity will be reduced from O(n*n*n) to O(n*n)

def naiveMaxSubarray(arr:list)->list:

# two nested loops to compare all possible pairs

# assume the arr is not empty. Otherwise, there is no max subarray

currentMax = arr[0]

i_max, j_max = 0, 0

n = len(arr)

for i in range(n):

# TODO: get rid of the sum function for better time complexity

for j in range(i,n):

if sum(arr[i:j]) > currentMax:

currentMax = sum(arr[i:j])

i_max, j_max = i, j

return [i_max, j_max-1]