codon/stdlib/algorithms/qsort.codon

105 lines
2.7 KiB
Python

def _med3[S,T](a: int, b: int, c: int, d: Array[T], k: Callable[[T], S]):
return ((b if (k(d[b]) < k(d[c])) else (c if k(d[a]) < k(d[c]) else a))
if (k(d[a]) < k(d[b])) else (b if (k(d[b]) > k(d[c])) else (c if k(d[a]) > k(d[c]) else a)))
def _swap[T](i: int, j: int, a: Array[T]):
a[i], a[j] = a[j], a[i]
def _vecswap[T](i: int, j: int, n: int, a: Array[T]):
while n > 0:
_swap(i, j, a)
i += 1
j += 1
n -= 1
def _qsort[S,T](arr: Array[T], frm: int, cnt: int, keyf: Callable[[T], S]):
if cnt <= 7:
i = frm + 1
while i < frm + cnt:
j = i
while j > frm and keyf(arr[j - 1]) > keyf(arr[j]):
_swap(j, j - 1, arr)
j -= 1
i += 1
return
mid = cnt // 2
lo = frm
hi = frm + cnt - 1
if cnt > 40:
s = cnt // 8
lo = _med3(lo, lo + s, lo + 2 * s, arr, keyf)
mid = _med3(mid - s, mid, mid + s, arr, keyf)
hi = _med3(hi - 2 * s, hi - s, hi, arr, keyf)
mid = _med3(lo, mid, hi, arr, keyf)
_swap(frm, mid, arr)
a = frm
b = a
c = frm + cnt - 1
d = c
while True:
while b <= c and keyf(arr[b]) <= keyf(arr[frm]):
if keyf(arr[b]) == keyf(arr[frm]):
_swap(a, b, arr)
a += 1
b += 1
while c >= b and keyf(arr[c]) >= keyf(arr[frm]):
if keyf(arr[c]) == keyf(arr[frm]):
_swap(c, d, arr)
d -= 1
c -= 1
if b > c:
break
_swap(b, c, arr)
b += 1
c -= 1
hi = frm + cnt
span = min(a - frm, b - a)
_vecswap(frm, b - span, span, arr)
span = min(d - c, hi - d - 1)
_vecswap(b, hi - span, span, arr)
span = b - a
if span > 1:
_qsort(arr, frm, span, keyf)
span = d - c
if span > 1:
_qsort(arr, hi - span, span, keyf)
def qsort_array[S,T](collection: Array[T], size: int, keyf: Callable[[T], S]):
"""
Pattern-defeating Quicksort
By Orson Peters, published at https://github.com/orlp/pdqsort
Sorts the array inplace.
"""
_qsort(collection, 0, size, keyf)
def qsort_inplace[S,T](collection: List[T], keyf: Callable[[T], S]):
"""
Pattern-defeating Quicksort
By Orson Peters, published at https://github.com/orlp/pdqsort
Sorts the list inplace.
"""
qsort_array(collection.arr, collection.len, keyf)
def qsort[S,T](collection: List[T], keyf: Callable[[T], S]) -> List[T]:
"""
Pattern-defeating Quicksort
By Orson Peters, published at https://github.com/orlp/pdqsort
Returns a sorted list.
"""
newlst = copy(collection)
qsort_inplace(newlst, keyf)
return newlst