Minimum Waiting - Algorithm

This algorithm is simple:

function minimumWaitingTime(times)
 sort times in ascending order
 totalWaiting := 0
 cumulativeTime := 0
 for i from 0 to length of times - 1
 totalWaiting := totalWaiting + cumulativeTime
 cumulativeTime := cumulativeTime + times[i]
 return totalWaiting

Time: $O(n \log n)$ for sorting. Space: $O(1)$ extra.