Given a list of strings, A task is to sort the strings in a case-insensitive manner. Given below are a few methods to solve the task.
Method #1: Using casefold()
Python3
# Python code to demonstrate to sort list of# strings in case insensitive manner# Initialising listini_list = ['akshat', 'garg', 'GeeksForGeeks', 'Alind', 'SIngh', 'manjeet', 'Munich']# Sorting list in case sensitive mannerres1 = sorted(ini_list)# Printing case-sensitiveprint("Case-sensitive sorted list", str(res1))# Sorting list in case-insensitive mannerres2 = sorted(ini_list, key=lambda s: s.casefold())# Printing case-senstive sorted listprint("Case-insensitive sorted list", str(res2)) |
Output
Case-sensitive sorted list ['Alind', 'GeeksForGeeks', 'Munich', 'SIngh', 'akshat', 'garg', 'manjeet'] Case-insensitive sorted list ['akshat', 'Alind', 'garg', 'GeeksForGeeks', 'manjeet', 'Munich', 'SIngh']
Time Complexity: O(nlogn)
Space Complexity: O(n)
Method #2: Using lower()
Python3
# Python code to demonstrate# to sort list of# strings in case insensitive manner# Initialising listini_list = ['akshat', 'garg', 'GeeksForGeeks', 'Alind', 'SIngh', 'manjeet', 'Munich']# Sorting list in case sensitive mannerini_list.sort()# Printing case-sensitiveprint("Case-sensitive sorted list", str(ini_list))# Sorting list in case-insensitive mannerini_list.sort(key=lambda x: x.lower())# Printing resultprint("Case-insensitive sorted list", str(ini_list)) |
Output
Case-sensitive sorted list ['Alind', 'GeeksForGeeks', 'Munich', 'SIngh', 'akshat', 'garg', 'manjeet'] Case-insensitive sorted list ['akshat', 'Alind', 'garg', 'GeeksForGeeks', 'manjeet', 'Munich', 'SIngh']
Time Complexity: O(nlogn)
Space Complexity: O(n)
Method #3: Using sort() method and str.lower() method:
Approach:
- In this example, we have a strings list containing five strings with different casing.
- We pass this list as an argument to the sort_strings_case_insensitive() function.
- Now store the result in the sorted_strings variable.
- Finally, we print the sorted_strings variable to see the resulting sorted list in a case-insensitive manner.
Example:
Python3
def sort_strings_case_insensitive(strings): strings.sort(key=str.lower) return strings# input stringstrings = ["apple", "Banana", "CHERRY", "durian", "EGGFRUIT"]sorted_strings = sort_strings_case_insensitive(strings)# Printing sorted stringprint(sorted_strings) |
Output
['apple', 'Banana', 'CHERRY', 'durian', 'EGGFRUIT']
Time Complexity: O(n log n), where n is the length of the list
Auxiliary Space: O(1)
Method #4: Use the merge sort algorithm with a key function to sort the list in a case-insensitive manner. The key function takes a string and returns its lowercase version, which will be used to compare the strings during the sorting process.
Here are the steps to implement this method:
- Define a merge_sort function that takes a list and a key function as arguments.
- If the length of the list is less than or equal to 1, return the list.
- Divide the list into two halves and recursively call merge_sort on each half.
- Merge the two sorted halves by comparing the elements using the key function.
- Return the merged list.
- Call the merge_sort function with the initial list and the key function as lambda x: x.lower().
- Print the sorted list.
Python3
# Python code to demonstrate to sort list of# strings in case insensitive manner# Define merge_sort function with key functiondef merge_sort(lst, key): # base-case if len(lst) <= 1: return lst # merge-sort logic mid = len(lst) // 2 left = merge_sort(lst[:mid], key) right = merge_sort(lst[mid:], key) return merge(left, right, key)# Define merge function to merge # two sorted lists using key functiondef merge(left, right, key): result = [] i, j = 0, 0 while i < len(left) and j < len(right): if key(left[i]) <= key(right[j]): result.append(left[i]) i += 1 else: result.append(right[j]) j += 1 result += left[i:] result += right[j:] return result# Initialising listini_list = ['akshat', 'garg', 'GeeksForGeeks', 'Alind', 'SIngh', 'manjeet', 'Munich']# Sorting list in case insensitive manner # using merge_sort with key functionres = merge_sort(ini_list, key=lambda x: x.lower())# Printing resultprint("Case-insensitive sorted list:", res) |
Output
Case-insensitive sorted list: ['akshat', 'Alind', 'garg', 'GeeksForGeeks', 'manjeet', 'Munich', 'SIngh']
Time complexity: O(n log n)
Auxiliary space: O(n).
Method #5: Comparing each element and placing at their correct position.
Sort the list in a case-insensitive manner by comparing the lowercase versions of the strings using the lower() method.
Python3
# Python code to demonstrate# to sort list of# strings in case insensitive manner# Initialising listini_list = ['akshat', 'garg', 'GeeksForGeeks', 'Alind', 'SIngh', 'manjeet', 'Munich']# Sorting list in case-sensitive manner using bubble sortfor i in range(len(ini_list)): for j in range(i+1, len(ini_list)): if ini_list[j].lower() < ini_list[i].lower(): ini_list[i], ini_list[j] = ini_list[j], ini_list[i]# Printing case-sensitiveprint("Case-sensitive sorted list", str(sorted(ini_list)))# Printing case-insensitive sorted list using bubble sortprint("Case-insensitive sorted list using bubble sort", str(ini_list)) |
Output
Case-sensitive sorted list ['Alind', 'GeeksForGeeks', 'Munich', 'SIngh', 'akshat', 'garg', 'manjeet'] Case-insensitive sorted list using bubble sort ['akshat', 'Alind', 'garg', 'GeeksForGeeks', 'manjeet', 'Munich', 'SIngh']
Time complexity: O(n * n)
Auxiliary space: O(n)
