Python Max Slice Sum
def max_slice_sum(a: list[int]) -> int:
    tmp = max_sum = float("-inf")
    for v in a:
        tmp = max(tmp + v, v)
        max_sum = max(max_sum, tmp)

    return int(max_sum)

This is a Kadane-style scan: keep the best running sum and the best overall sum while moving once through the array.