python 快速排序

a=[5,4,2,3,1]

print(a)
n=len(a)
l=0
r=n-1

while True:
    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
print(a)

[5, 4, 2, 3, 1]
[1, 2, 3, 4, 5]