Python – Sort Strings by Maximum ASCII value

Given strings list, perform sort by Maximum Character in String. 

Input : test_list = [“geeksforgeeks”, “is”, “best”, “cs”] 
Output : [“geeksforgeeks”, “is”, “cs”, “best”] 
Explanation : s = s = s < t, sorted by maximum character.

Input : test_list = [“apple”, “is”, “fruit”] 
Output : [“apple”, “is”, “fruit”] 
Explanation : p < s < t, hence order retained after sorting by max. character. 

Method #1 : Using sort() + max()

In this, sorting is performed using sort() and max() is used to get maximum character from Strings.

Python3

# Python3 code to demonstrate working of
# Sort Strings by Maximum Character
# Using sort() + max()

# get maximum character fnc.
def get_max(sub):

    # returns maximum character
    return ord(max(sub))


# initializing list
test_list = ["geeksforgeeks", "is", "best", "for", "cs"]

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

# performing sorting
test_list.sort(key=get_max)

# printing result
print("Sorted List : " + str(test_list))

Output

The original list is : ['geeksforgeeks', 'is', 'best', 'for', 'cs']
Sorted List : ['for', 'geeksforgeeks', 'is', 'cs', 'best']

Method #2 : Using sorted() + lambda + max()

In this, we perform task of sorting using sorted(), lambda and max() are used to input logic of getting maximum character.

Python3

# Python3 code to demonstrate working of
# Sort Strings by Maximum Character
# Using sorted() + lambda + max()

# initializing list
test_list = ["geeksforgeeks", "is", "best", "for", "cs"]

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

# performing sorting using sorted()
# lambda function provides logic
res = sorted(test_list, key=lambda sub: ord(max(sub)))

# printing result
print("Sorted List : " + str(res))

Output

The original list is : ['geeksforgeeks', 'is', 'best', 'for', 'cs']
Sorted List : ['for', 'geeksforgeeks', 'is', 'cs', 'best']

Time Complexity: O(n) -> built-in functions like max takes O(n)
Auxiliary Space: O(n)

Method 3: Using heapq.nlargest():

In this approach, we can use the heapq.nlargest() function to find the n largest elements of a list based on a given key function. We can pass k=len(test_list) to get all the elements of the list, and use a lambda function to return the maximum ASCII value of each string.

Python3

import heapq

test_list = ["geeksforgeeks", "is", "best", "cs"]
sorted_list = heapq.nlargest(len(test_list), test_list, key=lambda s: max(map(ord, s)))
print(sorted_list) # Output: ['geeksforgeeks', 'is', 'cs', 'best']

Output

['best', 'geeksforgeeks', 'is', 'cs']

Time Complexity: O(nmlog(k)), where n is the number of strings in the list, m is the length of the longest string, and k is the number of largest elements to be found. In this case, k is equal to len(test_list), so the time complexity is O(nmlog(n)).
Auxiliary Space: O(k), where k is the number of largest elements to be found. In this case, k is equal to len(test_list), so the space complexity is O(n).

Method #4: Using a custom function with list comprehension

Python3

# Python3 code to demonstrate working of
# Sort Strings by Maximum Character
# Using a custom function with list comprehension

# initializing list
test_list = ["geeksforgeeks", "is", "best", "for", "cs"]

# defining custom function to get maximum character ASCII value
def max_char_ascii(s):
    return ord(max(s))

# using list comprehension to create list of tuples
lst = [(s, max_char_ascii(s)) for s in test_list]

# sorting list of tuples based on second element (maximum character ASCII value)
res = sorted(lst, key=lambda x: x[1])

# extracting first element of each tuple (original string)
res = [t[0] for t in res]

# printing result
print("Sorted List : " + str(res))

Output

Sorted List : ['for', 'geeksforgeeks', 'is', 'cs', 'best']

Time complexity: O(n log n) (due to the use of the sorted() function)
Auxiliary space: O(n) (for the lst list of tuples)