import random
def fast_sort(a):
n=len(a)
l=0
r=n-1
while 1:
if a[l]>a[r]:
a[l],a[r]=a[r],a[l]
r=r-1
if l==r:
l=l+1
r=n-1
if l==n-1:
break
return a
a=list(range(20))
random.shuffle(a)
print(a)
print('-'*70)
print(fast_sort(a))
[19, 1, 18, 2, 6, 15, 9, 8, 5, 7, 16, 12, 13, 17, 14, 0, 4, 11, 3, 10]
----------------------------------------------------------------------
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]