Counting sort is a sorting technique based on keys between a specific range. It works by counting the number of objects having distinct key values (kind of hashing). Then doing some arithmetic to calculate the position of each object in the output sequence.
Python3
# Python program for counting sort # The main function that sort the given string arr[] in # alphabetical order def countSort(arr):
# The output character array that will have sorted arr
output = [ 0 for i in range ( 256 )]
# Create a count array to store count of individual
# characters and initialize count array as 0
count = [ 0 for i in range ( 256 )]
# For storing the resulting answer since the
# string is immutable
ans = ["" for _ in arr]
# Store count of each character
for i in arr:
count[ ord (i)] + = 1
# Change count[i] so that count[i] now contains actual
# position of this character in output array
for i in range ( 256 ):
count[i] + = count[i - 1 ]
# Build the output character array
for i in range ( len (arr)):
output[count[ ord (arr[i])] - 1 ] = arr[i]
count[ ord (arr[i])] - = 1
# Copy the output array to arr, so that arr now
# contains sorted characters
for i in range ( len (arr)):
ans[i] = output[i]
return ans
# Driver program to test above function arr = "geeksforgeeks"
ans = countSort(arr)
print ( "Sorted character array is %s" % ("".join(ans)))
# This code is contributed by Nikhil Kumar Singh |
Output:
Sorted character array is eeeefggkkorss
Time Complexity: O(n+k) where n is the number of elements in the input array and k is the range of input.
Auxiliary Space: O(n+k)
Please refer complete article on Counting Sort for more details!
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