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Print common characters of two Strings in alphabetical order

Python code to print common characters of two Strings in alphabetical order

Last Updated : 25 Jul, 2022

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Given two strings, print all the common characters in lexicographical order. If there are no common letters, print -1. All letters are lower case.

Examples:

Input :  string1 : geeks string2 : forgeeks Output : eegks Explanation: The letters that are common between  the two strings are e(2 times), g(1 time), k(1 time) and  s(1 time). Hence the lexicographical output is "eegks"  Input :  string1 : hhhhhello string2 : gfghhmh Output : hhh

This problem has existing solution please refer Print common characters of two Strings in alphabetical order link. We will solve this problem in python using intersection property and collections.Counter() module. Approach is simple,

Convert both strings into dictionary data type using Counter(str) method, which contains characters of string as key and their frequencies as value.

Now find common elements between two strings using intersection ( a&b ) property.

Resultant will also be an counter dictionary having common elements as keys and their common frequencies as value.

Use elements() method of counter dictionary to expand list of keys by their frequency number of times.

Sort the list and concatenate each character of output list without space to print resultant string.

Implementation:

Python3

   # Function to print common characters of two Strings 
# in alphabetical order 
from collections import Counter 
 
def common(str1,str2): 
     
    # convert both strings into counter dictionary 
    dict1 = Counter(str1) 
    dict2 = Counter(str2) 
 
    # take intersection of these dictionaries 
    commonDict = dict1 & dict2 
 
    if len(commonDict) == 0: 
        print (-1) 
        return
 
    # get a list of common elements 
    commonChars = list(commonDict.elements()) 
 
    # sort list in ascending order to print resultant 
    # string on alphabetical order 
    commonChars = sorted(commonChars) 
 
    # join characters without space to produce 
    # resultant string 
    print (''.join(commonChars)) 
 
# Driver program 
if __name__ == "__main__": 
    str1 = 'geeks'
    str2 = 'forgeeks'
    common(str1, str2) 
 
  

Output:

eegks

Time complexity : O(n)
Auxiliary Space : O(n)

Print common characters of two Strings in alphabetical order

S

Shashank Mishra

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Article Tags :

DSA
Python
Strings
Python string-programs
python-string

Practice Tags :

python
Strings

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