input: Write a python function to find the length of the largest subarray with a sum of zero.
  assert largest_subarray_sum([1, 2, -2, 4, -4]) == 5
  assert largest_subarray_sum([1, -1, 3, 2, -2, -3]) == 6
  assert largest_subarray_sum([1, 2, 3, 4, 5]) == 0
output: def largest_subarray_sum(arr):
      sum_map = {}
      max_len = 0
      curr_sum = 0
  
      for i in range(len(arr)):
          curr_sum += arr[i]
  
          if curr_sum == 0:
              max_len = i + 1
  
          if curr_sum in sum_map:
              max_len = max(max_len, i - sum_map[curr_sum])
          else:
              sum_map[curr_sum] = i
  
      return max_len