added 4 sorting algorithms

Author: Abhishek Kumar Maurya

.gitignore

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+/env/
+/__pycache__/
+/.vscode/

README.md

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+# Sorting algorithm visualizer
+
+Visualizing sorting algorithms, using the matplotlib library.
+
+Algorithms covered so far: 
+
+| Name | Function Name |
+| - |:-: |
+| Quick Sort | quick_sort |
+| Bubble Sort | bubble_sort |
+| Selection Sort | selection_sort |
+| Insertion Sort | insertion_sort |
+| Heap Sort | heap_sort |
+| Merge Sort | merge_sort |
+| Cocktail Sort | cocktail_sort |
+| Cycle Sort | cycle_sort |
+| Pigeonhole Sort | pigeonhole_sort |
+| Comb Sort | comb_sort |
+
+
+# Usage:
+
+Install
+
+```pip install -r requirements.txt``` 
+
+Run
+
+```python main.py function_name```
+
+Pass function name as a command line argument from list of functions above
+(in all lower case and spaces replaced by underscore).
+
+**For example:** 
+
+```python main.py quick_sort```
+
+# How to contribute
+
+**If you want to add a new sorting algorithm:**
+
+1. Code the algorithm in ```sorting.py```.
+2. Name the function appropriately, like ```quick_sort```, ```bubble_sort```.
+3. While coding the function, **do not use python lists**. Instead, use an ```Array``` object. The ```Array``` class is defined in ```sorting.py```. (See already implemented algorithms, for your reference)
+4. The ```Array``` object has ```swap```, ```set```, ```get_len```, ```get``` methods implemented. Feel free to implement any more, additional methods, that you may see fit.
+5. Make sure you add the sorting algorithm to the Readme file!
+6. Make sure your newly implemented algorithm works, by running `test.py` after appending it to the list of algorithms in `test.py`.

main.py

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+import sys
+import sorting as s
+import visualizer as vs
+import numpy as np
+import random
+
+
+def get_random_array(length):
+    n = list(range(length))
+    random.shuffle(n)
+    return n
+
+
+array_size = 50
+
+algorithms = [s.bubble_sort, s.heap_sort, s.selection_sort,
+              s.insertion_sort, s.quick_sort, s.insertion_sort, s.merge_sort, s.pigeonhole_sort,
+              s.cycle_sort, s.comb_sort, s.cocktail_sort]
+
+if len(sys.argv) < 2:
+    print('Usage:', 'python', sys.argv[0], 'function_name', '\n')
+    print('Choose from:', '\n')
+    for algorithm in algorithms:
+        print(algorithm.__name__)
+    print('\n')
+    sys.exit(0)
+
+algorithms = list(filter(lambda a: a.__name__ == sys.argv[1], algorithms))
+if (len(algorithms) == 0):
+    print('Method does not exist.')
+else:
+    algorithm = algorithms[0]
+    arr = s.Array(get_random_array(array_size))
+    algorithm(arr)
+    vs.show()

requirements.txt

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+numpy
+matplotlib