Algorithmic Python

Talk given as part of Python Pizza Hamburg 2019 and PyLadies Berlin December 2019 meetup.

Transcript

3. grokking algorithms
4. https://github.com/wwgberlin/algorithms //for each neighboring pair of integers in the slice //swap if left is larger than right //stop when nothing was swapped //complexity O(n2) func bubbleSort(s []int) { swapped := true for swapped { swapped = false for i := 1; i < len(s); i++ { if s[i-1] > s[i] { temp := s[i] s[i] = s[i-1] s[i-1] = temp swapped = true } } } }
6. Language Syntax is simple to learn so you can focus on the algorithms However it is a little harder to see what is happening beneath the suffice. Limited to how much optimisation you can do by Python itself
8. 0(1) 0(log n) 0(n) 0(n log n) 0(n^2) 0(2^n) 0(nl)
11. https://medium.com/@george.seif94/a-tour-of-the-top-5-sorting-algorithms-with-python-code-43ea9aa02889
12. def bubble_sort(arr): iteration_count = 0 for i in range (len(arr)): for idx in range(len(arr)-i-1): iteration_count += 1 if arr[idx] > arr[idx+1]: arr[idx], arr[idx+1] = arr[idx+1], arr[idx]
14. https://hackernoon.com/timsort-the-fastest-sorting-algorithm-youve-never-heard-of-36b28417f399
15. def insertion_sort(arr): for i in range(len(arr)): cursor = arr[i] pos = i while pos > 0 and arr[pos - 1] > cursor: # Swap the number down the list arr[pos] = arr[pos - 1] pos = pos - 1 # Break and do the final swap arr[pos] = cursor return arr
17. https://medium.com/@george.seif94/a-tour-of-the-top-5-sorting-algorithms-with-python-code-43ea9aa02889
18. def merge_sort(items): if len(items) <= 1: return items middle_index = len(items) // 2 left_split = items[:middle_index] right_split = items[middle_index:] left_sorted = merge_sort(left_split) right_sorted = merge_sort(right_split) return merge(left_sorted, right_sorted)
19. def merge(left, right): result =[] while (left and right): if left[0] < right[0]: result.append(left[0]) left.pop(0) else: result.append(right[0]) right.pop(0)
22. https://medium.com/@george.seif94/a-tour-of-the-top-5-sorting-algorithms-with-python-code-43ea9aa02889
23. def quick_sort(array, begin=0, end=None): if end is None: end = len(array) - 1 return quick_sort_recursion(array, begin, end)
24. def partition(array, begin, end): pivot_idx = begin for i in xrange(begin+1, end+1): if array[i] <= array[begin]: pivot_idx += 1 array[i], array[pivot_idx] = array[pivot_idx], array[i] array[pivot_idx], array[begin] = array[begin], array[pivot_idx] return pivot_idx def quick_sort_recursion(array, begin, end): if begin >= end: return pivot_idx = partition(array, begin, end) quick_sort_recursion(array, begin, pivot_idx-1) quick_sort_recursion(array, pivot_idx+1, end)
28. https://www.manning.com/books/grokk ing-algorithms https://www.codecademy.com/ https://www.khanacademy.org/ https://hackernoon.com/timsort-the -fastest-sorting-algorithm-youve-ne ver-heard-of-36b28417f399 https://medium.com/@george.seif94/a -tour-of-the-top-5-sorting-algorithms-w ith-python-code-43ea9aa02889