Care to elaborate on that "quadratic" comment?
Say you want to delete all elements in the second half of the array. The first N/2
iterations of your loop, no splicing happens. But on the N/2 + 1st
iteration, the splicing takes at least N/2 - 1
steps, as that many array elements need to be moved. On the N/2 + 2nd
iteration, the splicing takes at least N/2 - 2
steps. In total, you will be moving
array elements. If I've done my math correctly, the above sum equals (N2 - 2N + 4)/8. Which means your algorithm runs in Ω(N2) time.