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Warm up – Practice Quiz Questions

Warm up – Practice Quiz Questions. 1. Which sorting algorithm is used below? 79 58 24 6 19 42 58 79 24 6 19 42 24 58 79 6 19 42 6 24 58 79 19 42 6 19 24 58 79 42 6 19 24 42 58 79 Go to http://goo.gl/v0ffd. 2. Which sorting algorithm is used below? 63 53 87 79 94 19 63 53 87 79 94 19

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Warm up – Practice Quiz Questions

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  1. Warm up – Practice Quiz Questions 1. Which sorting algorithm is used below? • 79 58 24 6 19 42 • 58 79 24 6 19 42 • 24 58 79 6 19 42 • 6 24 58 79 19 42 • 6 19 24 58 79 42 • 6 19 24 42 58 79 Go to http://goo.gl/v0ffd 2. Which sorting algorithm is used below? • 63 53 87 79 94 19 • 63 53 87 79 94 19 • 63 53 87 79 94 19 • 63 53 87 79 94 19 • 53 63 87 79 94 19 • 53 63 87 19 79 94 • 19 53 63 79 87 94

  2. Don’t forget: You can copy-paste this slide into other presentations, and move or resize the poll. Poll: Which sorting algorithm is used for numb...

  3. Don’t forget: You can copy-paste this slide into other presentations, and move or resize the poll. Poll: Which sorting algorithm is used for numb...

  4. What does “efficiency” mean? • Measure of how long the algorithm takes to run to completion relative to the number of inputs it is given

  5. Why do we care? • “Because it helps computer programmers be more green and saves both time and energy which in turn saves money” • Inefficient algorithms require more calculations/comparisons/memory • Wasted time ( wasted money) • Wasted power ( being less “green”)

  6. How do we measure efficiency? • Big O notation  symbolic execution time • Formula for the growth rate of the time the algorithm takes to complete with respect to the amount of input data. • Approximation  no constants, no coefficients • Linear: • Quadratic: • Exponential: • Logarithmic: • Constant:

  7. Sorting Efficiency Lab • Use website to answer lab worksheet questions • Key Questions to think about: • What are the ideal properties of an efficient sorting algorithm? • What are the advantages and disadvantages of each sorting algorithm? • In what case(s) would you use one over another?

  8. Ideal Properties • Stable: Equal keys (values) aren't reordered. • Operates in place, requiring O(1) extra space. • Worst-case O(n log n) key comparisons. • Worst-case O(n) swaps (moves). • Adaptive: Speeds up to O(n) when data is nearly sorted or when there are few unique keys.

  9. Advantages/Disadvantages • Selection Sort • Advantages • O(1) extra space • O(n) swaps • Disadvantages • Not stable • comparisons • Not adaptive • Insertion Sort • Advantages • Stable • O(1) extra space • Adaptive: O(n) time when nearly sorted • Disadvantages • comparisons and swaps

  10. Advantages/Disadvantages • Merge Sort • Advantages • Stable • O(n log n) time • Disadvantages • O(n) extra space for arrays • Not adaptive

  11. When to use • Selection Sort • In place but not adaptive  real-time, memory limited applications with small data inputs • Insertion Sort • In place and adaptive  good for small, mostly sorted arrays • Merge Sort • Fast, not adaptive  variety of situations when memory is not an issue; better for sequential access

  12. Exit poll – Practice Quiz Questions • http://goo.gl/VNxVR

  13. Don’t forget: You can copy-paste this slide into other presentations, and move or resize the poll. Poll: Selection Sort always requires more comp...

  14. Don’t forget: You can copy-paste this slide into other presentations, and move or resize the poll. Poll: Insertion Sort always requires more swap...

  15. Don’t forget: You can copy-paste this slide into other presentations, and move or resize the poll. Poll: Merge Sort is always faster than Inserti...

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