Merge pull request #894 from neha030/dev24

counting sort added

Author: smv1999

Sorting Algorithms/counting_sort.py

@@ -0,0 +1,51 @@
+'''
+Counting sort is a sorting algorithm that sorts the elements of an
+array by counting the number of occurrences of each unique element in the array.
+In this program default 'k' is 1000.
+
+Algorithm
+In Counting Sort, we will follow the following step-wise process:
+
+First we will store the occurrence of elements in a count array.
+
+Modify the count array such that every index store the sum of the previous count.
+
+Traverse the given array from the end (so that stability maintains) and put the elements by checking our modified count array and the given input array.
+
+And take a final array (output) and store the elements.
+
+We get our sorted elements in the output array.
+'''
+
+def counting_sort(l, k=None):
+    #  creating an array for counting elements
+    if k == None:
+        arr = [0]*1000
+    else:
+        arr = [0]*(k+1)
+    # counting the occurrence of elements
+    for i in l:
+        arr[i]+=1
+    # generating sorted array
+    l=[]
+    for i in range(len(arr)):
+        l+=[i]*arr[i]
+    return l
+
+
+if __name__ == "__main__":
+    l = list(map(int,input("Enter the elements of the list to be sorted:").split()))
+    l = counting_sort(l)
+    print("List after sorting:",*l)
+
+'''
+INPUT
+Enter the elements of the list to be sorted:12 0 1 3 5 3 3 2 1 1
+OUTPUT
+List after sorting:0 1 1 1 2 3 3 3 5 12
+
+Worst Case Complexity: O(n+k)
+Best Case Complexity: O(n+k)
+Average Case Complexity: O(n+k)
+where n is size of an array , and k is element range of the array.
+'''