Added quick sort algorithm in python

SortingAlgorithms/quick_sort.py

@@ -0,0 +1,39 @@
+# 'Quick Sort'
+# Randomize Pivot to avoid worst case, currently pivot is last element
+
+
+def quickSort(A, si, ei):
+    if si < ei:
+        pi = partition(A, si, ei)
+        quickSort(A, si, pi-1)
+        quickSort(A, pi+1, ei)
+
+
+# 'Partition'
+# Utility function for partitioning the array(used in quick sort)
+def partition(A, si, ei):
+    x = A[ei]  # x is pivot, last element
+    i = (si-1)
+    for j in range(si, ei):
+        if A[j] <= x:
+            i += 1
+            A[i], A[j] = A[j], A[i]
+            A[i+1], A[ei] = A[ei], A[i+1]      
+    return i+1
+
+
+# Alternate Implementation
+# Warning --> As this function returns the array itself, assign it to some
+# Variable while calling. Example--> sorted_arr=quicksort(arr)  
+# 'Quick sort'
+
+
+def quicksort(arr):
+    if len(arr) <= 1:
+        return arr
+    pivot = arr[len(arr) / 2]
+    left = [x for x in arr if x < pivot]
+    middle = [x for x in arr if x == pivot]
+    right = [x for x in arr if x > pivot]
+    return quicksort(left) + middle + quicksort(right)
+