Given n strings, concatenate them in an order that produces the lexicographically smallest possible string.
Input : a = ["c", "cb", "cba"] Output : cbacbc Possible strings are ccbcba, ccbacb, cbccba, cbcbac, cbacbc and cbaccb. Among all these strings, cbacbc is the lexicographically smallest. Input : a = ["aa", "ab", "aaa"] Output : aaaaaab
One might think that sorting the given strings in the lexicographical order and then concatenating them produces the correct output. This approach produces the correct output for inputs like [“a”, “ab”, “abc”]. However, applying this method on [“c”, “cb”, “cba”] produces the wrong input and hence this approach is incorrect.
The correct approach is to use a regular sorting algorithm. When two strings a and b are compared to decide if they have to be swapped or not, do not check if a is lexicographically smaller than b or not. Instead check if appending b at the end of a produces a lexicographically smaller string or appending a at the end of b does. This approach works because we want the concatenated string to be lexicographically small, not the individual strings to be in the lexicographical order.
# Python 3 code to find the lexicographically
# smallest string
def lexSmallest(a, n):
# Sort strings using above compare()
a.sort(reverse = True)
# Concatenating sorted strings
answer = “”
for i in range( n):
answer += a[i]
# Driver code
if __name__ == “__main__”:
a = [ “c”, “cb”, “cba” ]
n = len(a)
# This code is contributed by ita_c
Time complexity : The above code runs inO(M * N * logN) where N is number of strings and M is maximum length of a string.
- Lexicographically smallest string formed by appending a character from the first K characters of a given string
- Lexicographically smallest string whose hamming distance from given string is exactly K
- Lexicographically smallest permutation of a string with given subsequences
- Queries to answer the X-th smallest sub-string lexicographically
- K-th lexicographically smallest unique substring of a given string
- Lexicographically smallest string formed by removing at most one character
- Find the lexicographically smallest string which satisfies the given condition
- Generate lexicographically smallest string of 0, 1 and 2 with adjacent swaps allowed
- Form lexicographically smallest string with minimum replacements having equal number of 0s, 1s and 2s
- Lexicographically smallest array after at-most K consecutive swaps
- Find the lexicographically smallest sequence which can be formed by re-arranging elements of second array
- Check if a string can be obtained by rotating another string 2 places
- Lexicographically smallest rotated sequence | Set 2
- Construct lexicographically smallest palindrome
- Lexicographically smallest substring with maximum occurrences containing a's and b's only
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to email@example.com. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.