# Do comparison sorts have to start at the beginning of the input?

Say I had an input $\langle3,17,15,9,1\rangle$, could I for example begin by comparing 1 with 3 so that 1 appeared at the start of the sorted sequence straight away or would I first have to compare 3 and 17 and then continue working from left to right with consecutive numbers? If the latter is correct, do I then have to keep returning to the start to continue comparing elements until I reach the fully sorted array? If this is the case, how is it possible to sort the input in $n-1$ (4) steps?