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Partitioning in Quicksort

Q. U. I. C. K. S. O. R. T. I. S. C. O. O. L. partition element. unpartitioned. left. partitioned. right. Partitioning in Quicksort. How do we partition in-place efficiently? Partition element = rightmost element. Scan from left for larger element.

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Partitioning in Quicksort

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  1. Q U I C K S O R T I S C O O L partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross.

  2. swap me partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. Q U I C K S O R T I S C O O L

  3. swap me partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. Q U I C K S O R T I S C O O L

  4. swap me partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. Q U I C K S O R T I S C O O L

  5. swap me swap me partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. Q U I C K S O R T I S C O O L

  6. partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C U I C K S O R T I S Q O O L

  7. swap me partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C U I C K S O R T I S Q O O L

  8. swap me partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C U I C K S O R T I S Q O O L

  9. swap me swap me partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C U I C K S O R T I S Q O O L

  10. partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C I I C K S O R T U S Q O O L

  11. partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C I I C K S O R T U S Q O O L

  12. partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C I I C K S O R T U S Q O O L

  13. partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C I I C K S O R T U S Q O O L

  14. swap me partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C I I C K S O R T U S Q O O L

  15. swap me partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C I I C K S O R T U S Q O O L

  16. swap me partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C I I C K S O R T U S Q O O L

  17. swap me partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. C I I C K S O R T U S Q O O L

  18. partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. swap with partitioning element pointers cross C I I C K S O R T U S Q O O L

  19. partition element unpartitioned left partitioned right Partitioning in Quicksort • How do we partition in-place efficiently? • Partition element = rightmost element. • Scan from left for larger element. • Scan from right for smaller element. • Exchange. • Repeat until pointers cross. partition is complete C I I C K L O R T U S Q O O S

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