diff --git a/BinarySeach.py b/BinarySeach.py deleted file mode 100644 index 9d09c6ba3..000000000 --- a/BinarySeach.py +++ /dev/null @@ -1,30 +0,0 @@ -def binarySearch(alist, item): - - first = 0 - last = len(alist)-1 - found = False - - while first<=last and not found: - - midpoint = (first + last)//2 - if alist[midpoint] == item: - found = True - print("Found [ at position: %s ]" % (alist.index(item) + 1)) - else: - - if item < alist[midpoint]: - - last = midpoint-1 - else: - first = midpoint+1 - - if found == False: - continue - # print("Not found") - return found -print("Enter numbers seprated by space") -s = input() -numbers = list(map(int, s.split())) -trgt =int( input('enter a single number to be found in the list ')) -binarySearch(numbers, trgt) - diff --git a/BubbleSort.py b/BubbleSort.py index 5a0388855..9f3579617 100644 --- a/BubbleSort.py +++ b/BubbleSort.py @@ -1,26 +1,39 @@ +import sys -array=[]; - -# input -print ("Enter any 6 Numbers for Unsorted Array : "); -for i in range(0, 6): - n=input(); - array.append(int(n)); - -# Sorting -print("") -for i in range(0, 6): - for j in range(0,5): - if (array[j]>array[j+1]): - temp=array[j]; - array[j]=array[j+1]; - array[j+1]=temp; - -# Output -for i in range(0,6): - print(array[i]); +def simple_bubble_sort(int_list): + count = len(int_list) + swapped = True + while (swapped): + swapped = False + for j in range(count - 1): + if (int_list[j] > int_list[j + 1]): + int_list[j], int_list[j + 1] = int_list[j + 1], int_list[j] + swapped = True + return int_list +def main(): + # Python 2's `raw_input` has been renamed to `input` in Python 3 + if sys.version_info.major < 3: + input_function = raw_input + else: + input_function = input + try: + print("Enter numbers separated by spaces:") + s = input_function() + inputs = list(map(int, s.split(' '))) + if len(inputs) < 2: + print('No Enough values to sort!') + raise Exception + except Exception as e: + print(e) + else: + sorted_input = simple_bubble_sort(inputs) + print('\nSorted list (min to max): {}'.format(sorted_input)) + +if __name__ == '__main__': + print('==== Bubble Sort ====\n') + main() diff --git a/InsertionSort.py b/InsertionSort.py index e0417a755..a577c4a81 100644 --- a/InsertionSort.py +++ b/InsertionSort.py @@ -1,25 +1,40 @@ -array=[]; - -# input -print ("Enter any 6 Numbers for Unsorted Array : "); -for i in range(0, 6): - n=input(); - array.append(int(n)); - -# Sorting -print("") -for i in range(1, 6): - temp=array[i] - j=i-1; - while(j>=0 and temp= 0 and temp < int_list[j]): + int_list[j + 1] = int_list[j] + j -= 1 + int_list[j + 1] = temp + + return int_list +def main(): + # Python 2's `raw_input` has been renamed to `input` in Python 3 + if sys.version_info.major < 3: + input_function = raw_input + else: + input_function = input + + try: + print("Enter numbers separated by spaces:") + s = input_function() + inputs = list(map(int, s.split(' '))) + if len(inputs) < 2: + print('No Enough values to sort!') + raise Exception + + except Exception as e: + print(e) + else: + sorted_input = simple_insertion_sort(inputs) + print('\nSorted list (min to max): {}'.format(sorted_input)) + +if __name__ == '__main__': + print('==== Insertion Sort ====\n') + main() diff --git a/LinearSearch.py b/LinearSearch.py index 6180eac5a..82595eded 100644 --- a/LinearSearch.py +++ b/LinearSearch.py @@ -1,21 +1,32 @@ -def sequentialSearch(alist, item): - pos = 0 - found = False - - while pos < len(alist) and not found: - - if alist[pos] == item: - found = True - print("Found") - else: - pos = pos+1 - if found == False: - print("Not found") - return found - -print("Enter numbers seprated by space") -s = input() -numbers = list(map(int, s.split())) -trgt =int( input('enter a single number to be found in the list ')) -sequentialSearch(numbers, trgt) +import sys + +def sequential_search(alist, target): + for index, item in enumerate(alist): + if item == target: + print("Found target {} at index {}".format(target, index)) + break + else: + print("Not found") + + +def main(): + # Python 2's `raw_input` has been renamed to `input` in Python 3 + if sys.version_info.major < 3: + input_function = raw_input + else: + input_function = input + + try: + print("Enter numbers separated by spaces") + s = input_function() + inputs = list(map(int, s.split(' '))) + target = int(input_function('\nEnter a number to be found in list: ')) + except Exception as e: + print(e) + else: + sequential_search(inputs, target) + +if __name__ == '__main__': + print('==== Linear Search ====\n') + main() diff --git a/MergeSort.py b/MergeSort.py index 7ce144dc7..ff3a31c70 100644 --- a/MergeSort.py +++ b/MergeSort.py @@ -1,36 +1,59 @@ -def mergeSort(alist): - print("Splitting ",alist) - if len(alist)>1: - mid = len(alist)//2 - lefthalf = alist[:mid] - righthalf = alist[mid:] - mergeSort(lefthalf) - mergeSort(righthalf) - i=0 - j=0 - k=0 - while i < len(lefthalf) and j < len(righthalf): - if lefthalf[i] < righthalf[j]: - alist[k]=lefthalf[i] - i=i+1 +import sys + + +def merge_sort(alist): + print("Splitting ", alist) + if len(alist) > 1: + mid = len(alist) // 2 + left_half = alist[:mid] + right_half = alist[mid:] + merge_sort(left_half) + merge_sort(right_half) + i = j = k = 0 + + while i < len(left_half) and j < len(right_half): + if left_half[i] < right_half[j]: + alist[k] = left_half[i] + i += 1 else: - alist[k]=righthalf[j] - j=j+1 - k=k+1 + alist[k] = right_half[j] + j += 1 + k += 1 - while i < len(lefthalf): - alist[k]=lefthalf[i] - i=i+1 - k=k+1 + while i < len(left_half): + alist[k] = left_half[i] + i += 1 + k += 1 - while j < len(righthalf): - alist[k]=righthalf[j] - j=j+1 - k=k+1 - print("Merging ",alist) + while j < len(right_half): + alist[k] = right_half[j] + j += 1 + k += 1 + print("Merging ", alist) + return alist -print("Enter numbers seprated by space") -s = input() -numbers = list(map(int, s.split())) -mergeSort(numbers) +def main(): + # Python 2's `raw_input` has been renamed to `input` in Python 3 + if sys.version_info.major < 3: + input_function = raw_input + else: + input_function = input + + try: + print("Enter numbers separated by spaces:") + s = input_function() + inputs = list(map(int, s.split(' '))) + if len(inputs) < 2: + print('No Enough values to sort!') + raise Exception + + except Exception as e: + print(e) + else: + sorted_input = merge_sort(inputs) + print('\nSorted list (min to max): {}'.format(sorted_input)) + +if __name__ == '__main__': + print('==== Merge Sort ====\n') + main() diff --git a/QuickSort.py b/QuickSort.py index 89db5a6a3..2d922a3de 100644 --- a/QuickSort.py +++ b/QuickSort.py @@ -1,31 +1,41 @@ +import sys -def quicksort(A, p, r): + +def quick_sort(A, p, r): if p < r: q = partition(A, p, r) - quicksort(A, p, q - 1) - quicksort(A, q + 1, r) + quick_sort(A, p, q - 1) + quick_sort(A, q + 1, r) + return A def partition(A, p, r): - x = A[r] i = p - 1 for j in range(p, r): - if A[j] <= x: + if A[j] <= A[r]: i += 1 - tmp = A[i] - A[i] = A[j] - A[j] = tmp - tmp = A[i+1] - A[i+1] = A[r] - A[r] = tmp + A[i], A[j] = A[j], A[i] + A[i + 1], A[r] = A[r], A[i + 1] return i + 1 -if __name__ == "__main__": - print('Enter values seperated by space:') - A = [int (item) for item in input().split(' ')] - # A = [23, 45, 43, 12, 67, 98, 123, 99] - # partition(A, 0, 7) - print(A) - quicksort(A, 0, 7) - print(A) +def main(): + # Python 2's `raw_input` has been renamed to `input` in Python 3 + if sys.version_info.major < 3: + input_function = raw_input + else: + input_function = input + + try: + print("Enter numbers separated by spaces") + s = input_function() + inputs = list(map(int, s.split(' '))) + except Exception as e: + print(e) + else: + sorted_input = quick_sort(inputs, 0, len(inputs) - 1) + print('\nSorted list (min to max): {}'.format(sorted_input)) + +if __name__ == '__main__': + print('==== Quick Sort ====\n') + main() diff --git a/README.md b/README.md index 4c8df87ad..8fcf1a656 100644 --- a/README.md +++ b/README.md @@ -1,2 +1,89 @@ -# Python- -All Algorithms implemented in Python +# The Algorithms - Python + +### All algorithms implemented in Python (for education) + +These are for demonstration purposes only. There are many implementations of sorts in the Python standard library that are much better for performance reasons. + +## Sorting Algorithms + +### Binary +Add comments here + +### Bubble +![alt text][bubble-image] + +From [Wikipedia][bubble-wiki]: Bubble sort, sometimes referred to as sinking sort, is a simple sorting algorithm that repeatedly steps through the list to be sorted, compares each pair of adjacent items and swaps them if they are in the wrong order. The pass through the list is repeated until no swaps are needed, which indicates that the list is sorted. + +__Properties__ +* Worst case performance O(n^2) +* Best case performance O(n) +* Average case performance O(n^2) + +###### View the algorithm in [action][bubble-toptal] + + + +### Insertion +![alt text][insertion-image] + +From [Wikipedia][insertion-wiki]: Insertion sort is a simple sorting algorithm that builds the final sorted array (or list) one item at a time. It is much less efficient on large lists than more advanced algorithms such as quicksort, heapsort, or merge sort. + +__Properties__ +* Worst case performance O(n^2) +* Best case performance O(n) +* Average case performance O(n^2) + +###### View the algorithm in [action][insertion-toptal] + + +## Merge +![alt text][merge-image] + +From [Wikipedia][merge-wiki]: In computer science, merge sort (also commonly spelled mergesort) is an efficient, general-purpose, comparison-based sorting algorithm. Most implementations produce a stable sort, which means that the implementation preserves the input order of equal elements in the sorted output. Mergesort is a divide and conquer algorithm that was invented by John von Neumann in 1945. + +__Properties__ +* Worst case performance O(n log n) +* Best case performance O(n) +* Average case performance O(n) + + +###### View the algorithm in [action][merge-toptal] + +## Quick +![alt text][quick-image] + +From [Wikipedia][quick-wiki]: Quicksort (sometimes called partition-exchange sort) is an efficient sorting algorithm, serving as a systematic method for placing the elements of an array in order. + +__Properties__ +* Worst case performance O(n^2) +* Best case performance O(n log n) or O(n) with three-way partition +* Average case performance O(n^2) + +###### View the algorithm in [action][quick-toptal] + + +## Search Algorithms + +### Linear +Add comments here + +## Ciphers + +### Caesar +Add comments here + +[bubble-toptal]: https://www.toptal.com/developers/sorting-algorithms/bubble-sort +[bubble-wiki]: https://en.wikipedia.org/wiki/Bubble_sort +[bubble-image]: https://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Bubblesort-edited-color.svg/220px-Bubblesort-edited-color.svg.png "Bubble Sort" + +[insertion-toptal]: https://www.toptal.com/developers/sorting-algorithms/insertion-sort +[insertion-wiki]: https://en.wikipedia.org/wiki/Insertion_sort +[insertion-image]: https://upload.wikimedia.org/wikipedia/commons/7/7e/Insertionsort-edited.png "Insertion Sort" + +[quick-toptal]: https://www.toptal.com/developers/sorting-algorithms/quick-sort +[quick-wiki]: https://en.wikipedia.org/wiki/Quicksort +[quick-image]: https://upload.wikimedia.org/wikipedia/commons/6/6a/Sorting_quicksort_anim.gif "Quick Sort" + +[merge-toptal]: https://www.toptal.com/developers/sorting-algorithms/merge-sort +[merge-wiki]: https://en.wikipedia.org/wiki/Merge_sort +[merge-image]: https://upload.wikimedia.org/wikipedia/commons/c/cc/Merge-sort-example-300px.gif "Merge Sort" diff --git a/SelectionSort.py b/SelectionSort.py deleted file mode 100644 index 6f3b9fe0d..000000000 --- a/SelectionSort.py +++ /dev/null @@ -1,20 +0,0 @@ -def selectionsort( aList ): - for i in range( len( aList ) ): - least = i - for k in range( i + 1 , len( aList ) ): - if aList[k] < aList[least]: - least = k - - aList = swap( aList, least, i ) - print(aList) - -def swap( A, x, y ): - tmp = A[x] - A[x] = A[y] - A[y] = tmp - return A - -print ("Enter numbers seprated by comma ") -response = input() -aList = [int(item) for item in (response.split(','))] -selectionsort(aList) diff --git a/binary_seach.py b/binary_seach.py new file mode 100644 index 000000000..a48762863 --- /dev/null +++ b/binary_seach.py @@ -0,0 +1,129 @@ +""" +This is pure python implementation of binary search algorithm + +For doctests run following command: +python -m doctest -v selection_sort.py +or +python3 -m doctest -v selection_sort.py + +For manual testing run: +python binary_search.py +""" +from __future__ import print_function +import bisect + + +def assert_sorted(collection): + """Check if collection is sorted. If not raises :py:class:`ValueError` + + :param collection: collection + :return: True if collection is sorted + :raise: :py:class:`ValueError` if collection is not sorted + + Examples: + >>> assert_sorted([0, 1, 2, 4]) + True + + >>> assert_sorted([10, -1, 5]) + Traceback (most recent call last): + ... + ValueError: Collection must be sorted + """ + if collection != sorted(collection): + raise ValueError('Collection must be sorted') + return True + + +def binary_search(sorted_collection, item): + """Pure implementation of binary search algorithm in Python + + :param sorted_collection: some sorted collection with comparable items + :param item: item value to search + :return: index of found item or None if item is not found + + Examples: + >>> binary_search([0, 5, 7, 10, 15], 0) + 0 + + >>> binary_search([0, 5, 7, 10, 15], 15) + 4 + + >>> binary_search([0, 5, 7, 10, 15], 5) + 1 + + >>> binary_search([0, 5, 7, 10, 15], 6) + + >>> binary_search([5, 2, 1, 5], 2) + Traceback (most recent call last): + ... + ValueError: Collection must be sorted + """ + assert_sorted(sorted_collection) + left = 0 + right = len(sorted_collection) - 1 + + while left <= right: + midpoint = (left + right) // 2 + current_item = sorted_collection[midpoint] + if current_item == item: + return midpoint + else: + if item < current_item: + right = midpoint - 1 + else: + left = midpoint + 1 + return None + + +def binary_search_std_lib(sorted_collection, item): + """Pure implementation of binary search algorithm in Python using stdlib + + :param sorted_collection: some sorted collection with comparable items + :param item: item value to search + :return: index of found item or None if item is not found + + Examples: + >>> binary_search_std_lib([0, 5, 7, 10, 15], 0) + 0 + + >>> binary_search_std_lib([0, 5, 7, 10, 15], 15) + 4 + + >>> binary_search_std_lib([0, 5, 7, 10, 15], 5) + 1 + + >>> binary_search_std_lib([0, 5, 7, 10, 15], 6) + + >>> binary_search_std_lib([5, 2, 1, 5], 2) + Traceback (most recent call last): + ... + ValueError: Collection must be sorted + """ + assert_sorted(sorted_collection) + index = bisect.bisect_left(sorted_collection, item) + if index != len(sorted_collection) and sorted_collection[index] == item: + return index + return None + + +if __name__ == '__main__': + import sys + # For python 2.x and 3.x compatibility: 3.x has not raw_input builtin + # otherwise 2.x's input builtin function is too "smart" + if sys.version_info.major < 3: + input_function = raw_input + else: + input_function = input + + user_input = input_function('Enter numbers separated by coma:\n') + collection = [int(item) for item in user_input.split(',')] + + target_input = input_function( + 'Enter a single number to be found in the list:\n' + ) + target = int(target_input) + result = binary_search(collection, target) + if result is not None: + print('{} found at positions: {}'.format(target, result)) + else: + print('Not found') diff --git a/selection_sort.py b/selection_sort.py new file mode 100644 index 000000000..4de19d230 --- /dev/null +++ b/selection_sort.py @@ -0,0 +1,51 @@ +""" +This is pure python implementation of selection sort algorithm + +For doctests run following command: +python -m doctest -v selection_sort.py +or +python3 -m doctest -v selection_sort.py +""" +from __future__ import print_function + +def selection_sort(sortable): + """Pure implementation of selection sort algorithm in Python + + Examples: + >>> selection_sort([0, 5, 3, 2, 2]) + [0, 2, 2, 3, 5] + + >>> selection_sort([]) + [] + + >>> selection_sort([-2, -5, -45]) + [-45, -5, -2] + + :param sortable: some mutable ordered collection with heterogeneous + comparable items inside + :return: the same collection ordered by ascending + """ + length = len(sortable) + for i in range(length): + least = i + for k in range(i + 1, length): + if sortable[k] < sortable[least]: + least = k + sortable[least], sortable[i] = ( + sortable[i], sortable[least] + ) + return sortable + + +if __name__ == '__main__': + import sys + # For python 2.x and 3.x compatibility: 3.x has not raw_input builtin + # otherwise 2.x's input builtin function is too "smart" + if sys.version_info.major < 3: + input_function = raw_input + else: + input_function = input + + user_input = input_function('Enter numbers separated by coma:\n') + unsorted = [int(item) for item in user_input.split(',')] + print(selection_sort(unsorted))