Maximum subarray sum

After a long road trip you log one mood score per day, an integer that can be negative on rough days. You want to find the most enjoyable stretch of the trip: the consecutive block of one or more days whose scores add up to the largest total. Given the daily scores in order, return that maximum total. The list is non-empty. For example, [-2, 4, -1, 5] gives 8 for the stretch [4, -1, 5].