46 lines
925 B
Ruby
46 lines
925 B
Ruby
# 3 way quick sort (Quick sort optimized for duplicates)
|
|
#In 3 Way QuickSort, an array arr[l..r] is divided in 3 parts:
|
|
#a) arr[l..i] elements less than pivot.
|
|
#b) arr[i+1..j-1] elements equal to pivot.
|
|
#c) arr[j..r] elements greater than pivot
|
|
|
|
def quick_sort(a,lo,hi)
|
|
if lo<hi
|
|
temp=partition(a,lo,hi)
|
|
l=temp[0]
|
|
r=temp[1]
|
|
quick_sort(a,lo,l-1)
|
|
quick_sort(a,r+1,hi)
|
|
end
|
|
end
|
|
|
|
def partition(a,lo,hi)
|
|
pivot=a[lo]
|
|
i=lo+1
|
|
lt=lo
|
|
gt=hi
|
|
|
|
while(i<=gt)
|
|
if a[i]< pivot
|
|
temp=a[lt]
|
|
a[lt]=a[i]
|
|
a[i]=temp
|
|
lt+=1
|
|
i+=1
|
|
elsif a[i]>pivot
|
|
temp=a[i]
|
|
a[i]=a[gt]
|
|
a[gt]=temp
|
|
gt-=1
|
|
else
|
|
i+=1
|
|
end
|
|
end
|
|
return lt,gt
|
|
end
|
|
|
|
|
|
a = [4, 4, 2, 4, 2, 4, 1, 2, 4, 1, 2, 2, 2, 2, 4, 1, 4, 4, 4]
|
|
|
|
quick_sort(a,0,18)
|
|
print a |