Python/sorts/countingsort.py

43 lines
1.2 KiB
Python

from __future__ import print_function
# Python program for counting sort
# This is the main function that sort the given string arr[] in
# in the 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 inidividul
# 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 = "thisisthestring"
ans = countSort(arr)
print ("Sorted string array is %s" %("".join(ans)))