Tuesday, 12 February 2008


Quicksort is an algorithm developed by C. A. R. Hoare in 1960 to sort a sequence of elements into order. Quicksort works by dividing a sequence into two sub-sequences.

An element is selected from the sequence and called the pivot. The sequence is then re-arranged so all elements with a value less than the pivot are before the pivot and all elements with a greater value are after it.

The sub-sequences before and after the pivot are then recursively sorted.

Implementation in Redcode:
          org    qsort

stack equ outer-2
pivot equ outer-1

outer mov p, <stack
mov {p, pivot

inner slt pivot, >p
y djn inner, #LENGTH-1
jmz done, y
mov <p, *p
mov {p, @p
djn inner, y

done mov.a @stack, p
mov.ba p, @stack
mov pivot, >p

qsort mov.ab p, y
sub.b p, y

slt y, #2
jmp outer, <y

mov.f >stack, p
jmn qsort, p


No comments: