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