 In terms of moves, merge sort's worst case complexity is O("n" log "n")—the same complexity as quicksort's best case, and merge sort's best case takes about half as many iterations as the worst case.Merge sort is more efficient than quicksort for some types of lists if the data to be sorted can only be efficiently accessed sequentially, and is thus popular in languages such as Lisp, where sequentially accessed data structures are very common.Unlike some (efficient) implementations of quicksort, merge sort is a stable sort.