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Hashing in Action

Hashing in Action. Nattee Niparnan. Operation. Insert Depends on Find Delete Depends on Find, also. Find. Find a room that should contain the value. Simple Hash. Room index. Hash Function. Name. Trying to add. Add Alice. 1. Hash Function. Alice. Add Alice. 1. Hash Function.

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Hashing in Action

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  1. Hashing in Action Nattee Niparnan

  2. Operation • Insert • Depends on Find • Delete • Depends on Find, also

  3. Find • Find a room that should contain the value

  4. Simple Hash Room index Hash Function Name

  5. Trying to add

  6. Add Alice 1 Hash Function Alice

  7. Add Alice 1 Hash Function Alice

  8. Add Peter 9 Hash Function Peter

  9. Add Bob 2 Hash Function Bob

  10. Find Vicky 7 Hash Function Vicky

  11. Add Vicky 7 Hash Function Vicky

  12. Collision Resolution

  13. Two approach • Separate chaining • Create another “space” for the collision • Need more memory • Open addressing • Try to squeeze in another room • Does not need more memory • Deletion problem

  14. Separate chaining • Try adding • The new 3 guys will collide with “Alice”

  15. Add Adam Adam Collide!! 1 Hash Function

  16. We use “LinkedList” as the storage Adam Alice 1 Bob Hash Function Vicky Peter

  17. Add Adam as a new node Adam Alice Adam 1 Bob Hash Function Vicky Peter

  18. Add Able as a new node Able Alice Adam 1 Bob Hash Function Able Vicky Peter

  19. Open Addressing • Find another room • Linear Probing (LP) • Quadratic Probing (QP) • Double Hashing (DH)

  20. Open Addressing Mechanism • Each time a collision occur, • Count the number of collision • “ColCount” • Instead of using Hash1(x) as the room index • Use instead “Hash1(x) + F(ColCount)” • F(ColCount) is the open addressing function

  21. Linear Probing • Use next room • F(ColCount) = ColCount;

  22. Adding Adam in LP

  23. Add Adam in LP Adam Collide!! 1 Hash Function

  24. Add Adam in LP Adam 2 Hash Function Update!!

  25. Add Adam in LP Adam 2 Collide!! Again Hash Function

  26. Add Adam in LP Adam 3 Hash Function Update!!

  27. Add Adam in LP Adam 3 Hash Function Free Space

  28. Adding Able in LP

  29. Add Able in LP Able Collide!! 1 Hash Function

  30. Add Able in LP Able 2 Hash Function Update!!

  31. Add Able in LP Able 2 Collide!! Again Hash Function

  32. Add Able in LP Able 3 Hash Function Update!!

  33. Add Able in LP Able 3 Hash Function Collide Again

  34. Add Able in LP Able 4 Hash Function Free Space Update!!

  35. Quadratic Probing • Jump by square • F(ColCount) = ColCount * ColCount;

  36. Adding Adam in QP

  37. Add Adam in QP Adam Collide!! 1 Hash Function

  38. Add Adam in QP Adam 2 Hash Function Update!!

  39. Add Adam in QP Adam 2 Collide!! Again Hash Function

  40. Add Adam in QP Adam 5 Hash Function Update!!

  41. Add Adam in QP Adam 5 Hash Function Free Space

  42. Adding Able in QP

  43. Add Able in QP Able Collide!! 1 Hash Function

  44. Add Able in QP Able 2 Hash Function Update!!

  45. Add Able in QP Able 2 Collide!! Again Hash Function

  46. Add Able in QP Able 5 Hash Function Update!!

  47. Add Able in QP Able 5 Hash Function Collide Again!!

  48. Add Able in QP Able 10 Hash Function Update!!

  49. Add Able in QP Able 5 Hash Function Free Space

  50. Double Hashing • Jump by another hash function • F(ColCount) = ColCount * Hash2(x);

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