quick sort

Author: codebasics

Algorithms/3_QuickSort/quick_sort.py

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+# implementation of quick sort in python using hoare partition scheme
+
+def swap(a, b, arr):
+    if a!=b:
+        tmp = arr[a]
+        arr[a] = arr[b]
+        arr[b] = tmp
+
+def quick_sort(elements, start, end):
+    if start < end:
+        pi = partition(elements, start, end)
+        quick_sort(elements, start, pi-1)
+        quick_sort(elements, pi+1, end)
+
+def partition(elements, start, end):
+    pivot_index = start
+    pivot = elements[pivot_index]
+
+    while start < end:
+        while start < len(elements) and elements[start] <= pivot:
+            start+=1
+
+        while elements[end] > pivot:
+            end-=1
+
+        if start < end:
+            swap(start, end, elements)
+
+    swap(pivot_index, end, elements)
+
+    return end
+
+
+if __name__ == '__main__':
+    elements = [11,9,29,7,2,15,28]
+    # elements = ["mona", "dhaval", "aamir", "tina", "chang"]
+    quick_sort(elements, 0, len(elements)-1)
+    print(elements)
+
+    tests = [
+        [11,9,29,7,2,15,28],
+        [3, 7, 9, 11],
+        [25, 22, 21, 10],
+        [29, 15, 28],
+        [],
+        [6]
+    ]
+
+    for elements in tests:
+        quick_sort(elements, 0, len(elements)-1)
+        print(f'sorted array: {elements}')
+
+

Algorithms/3_QuickSort/quick_sort_exercise.md

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+### Exercise: Quick Sort
+Implement quick sort using lumoto partition scheme. This partition scheme is explained in the video tutorial, you need to write python code to implement it.
+Check the pseudo code here: https://en.wikipedia.org/wiki/Quicksort Check the section Lomuto partition scheme
+ 
+ [Solution](https://github.com/codebasics/py/blob/master/Algorithms/3_QuickSort/quick_sort_exercise_soluiton_lomuto.py)
+
+
+ 

Algorithms/3_QuickSort/quick_sort_exercise_soluiton_lomuto.py

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+# This implements quick sort using lomuto partition scheme
+
+def swap(a, b, arr):
+    if a!=b:
+        tmp = arr[a]
+        arr[a] = arr[b]
+        arr[b] = tmp
+
+def quick_sort(elements, start, end):
+    if len(elements)== 1:
+        return
+    if start < end:
+        pi = partition(elements, start, end)
+        quick_sort(elements, start, pi-1)
+        quick_sort(elements, pi+1, end)
+
+def partition(elements, start, end):
+    pivot = elements[end]
+    p_index = start
+
+    for i in range(start, end):
+        if elements[i] <= pivot:
+            swap(i, p_index, elements)
+            p_index += 1
+
+    swap(p_index, end, elements)
+
+    return p_index
+
+
+if __name__ == '__main__':
+    tests = [
+        [11,9,29,7,2,15,28],
+        [3, 7, 9, 11],
+        [25, 22, 21, 10],
+        [29, 15, 28],
+        [],
+        [6]
+    ]
+    # elements = ["mona", "dhaval", "aamir", "tina", "chang"]
+
+    for elements in tests:
+        quick_sort(elements, 0, len(elements)-1)
+        print(f'sorted array: {elements}')