Python | Sort each String in String list

Sometimes, while working with Python, we can have a problem in which we need to perform the sort operation in all the Strings that are present in a list. This problem can occur in general programming and web development. Let's discuss certain ways in which this problem can be solved. 

Method #1 : Using list comprehension + sorted() + join() This is one way in which this problem can be solved. In this, we use sorted() functionality to perform sort operation and join() is used to reconstruct the string list. 

# Python3 code to demonstrate working of
# Sort Strings in String list
# using list comprehension + sorted() + join()

# initialize list 
test_list = ['gfg', 'is', 'good']

# printing original list 
print("The original list : " + str(test_list))

# Sort Strings in String list
# using list comprehension + sorted() + join()
res = [''.join(sorted(ele)) for ele in test_list]

# printing result
print("List after string sorting : " + str(res))

The original list : ['gfg', 'is', 'good']
List after string sorting : ['fgg', 'is', 'dgoo']

Time Complexity: O(n*nlogn) where n is the number of elements in the string list. The list comprehension + sorted() + join() is used to perform the task and it takes O(n*nlogn) time.
Auxiliary Space: O(n) additional space of size n is created where n is the number of elements in the string list.

  Method #2 : Using map() + sorted() + join() + lambda The combination of above method can also be used to perform this task. In this, we perform the functionality of traversal using map() and lambda rather than list comprehension.

# Python3 code to demonstrate working of
# Sort Strings in String list
# using map() + sorted() + join() + lambda

# initialize list 
test_list = ['gfg', 'is', 'good']

# printing original list 
print("The original list : " + str(test_list))

# Sort Strings in String list
# using map() + sorted() + join() + lambda
res = list(map(lambda ele: "".join(sorted(ele)), test_list))

# printing result
print("List after string sorting : " + str(res))

The original list : ['gfg', 'is', 'good']
List after string sorting : ['fgg', 'is', 'dgoo']

Time Complexity: O(n*nlogn), where n is the length of the input list. This is because we’re using map() + sorted() + join() + lambda which has a time complexity of O(n*nlogn) in the worst case.
Auxiliary Space: O(n), as we’re using additional space res other than the input list itself with the same size of input list.

Method #3: Using reduce()

Algorithm

1. Initialize an empty list res
2. For each string s in test_list, do the following:
   a. Sort the characters in s using sorted()
   b. Join the sorted characters back together into a string using join()
   c. Append the sorted string to res
3. Return res.

# Python3 code to demonstrate working of
# Sort Strings in String list
# using reduce() + sorted() + join()

from functools import reduce

# initialize list 
test_list = ['gfg', 'is', 'good']

# printing original list 
print("The original list : " + str(test_list))

# Sort Strings in String list
# using reduce() + sorted() + join()
res = reduce(lambda x, y: x + [''.join(sorted(y))], test_list, [])

# printing result
print("List after string sorting : " + str(res))
#This code is contributed by Vinay Pinjala.

The original list : ['gfg', 'is', 'good']
List after string sorting : ['fgg', 'is', 'dgoo']

Time complexity: O(n * m * log(m)), where n is the length of the list test_list and m is the maximum length of a string in test_list. This is because sorted() takes O(m * log(m)) time to sort each string in test_list, and reduce() takes O(n) time to iterate over each element in test_list.

Space complexity: O(n * m), where n is the length of the list test_list and m is the maximum length of a string in test_list. This is because the reduce() function creates a new list res with one element for each element in test_list, and each element in res takes up to m characters.