Included count sort in sorting.py

sorting and basics/sorting.py

@@ -87,6 +87,38 @@ def insertionsort(a):
         a[j] = item
     return a
 
+def countsort(a):
+    """ count sort implementation
+    >>> countsort([6,4,8,2,1,9,10])
+    [1,2,4,6,8,9,10]
+
+    Time complexity = O(n+k)
+    Space complexity = O(n+k)  
+    where k is the number of elements in a particular range 
+          n is the length of the input array
+    """
+    #to figure out the range of numbers in the array
+    maxval=max(a)
+    minval=min(a)
+    numberOfElements=maxval-minval+1
+    countArray=[0]*numberOfElements
+    resultArray=[0]*len(a)
+
+    #finding count of each element in the array and storing them in count array
+    for item in a:
+        countArray[item-minval]+=1
+    for item in range(1,len(countArray)):
+        countArray[item]+=countArray[item-1]
+
+    #storing in result array
+    for item in range(len(a)-1,-1,-1):
+        resultArray[countArray[a[item]-minval]-1]=a[item]
+        countArray[a[item]-minval]-=1
+    #sorted input array
+    for item in range(len(a)):
+        a[item]=resultArray[item]
+    return a
+
 if __name__ == "__main__":
     import doctest
     doctest.testmod(verbose=True)