Longest common anagram subsequence from N strings

Given N strings. Find the longest possible subsequence from each of these N strings such that they are anagram to each other. The task is to print the lexicographically largest subsequence among all the subsequences.

Examples:

Input: s[] = { geeks, esrka, efrsk }
Output: ske
First string has “eks”, Second string has “esk”, third string has “esk”. These three are anagrams. “ske” is lexoigrapically large.

Input: string s[] = { loop, lol, olive }
Output: ol

Approach :

  • Make a 2-D array of n*26 to store the frequency of each character in string.
  • After making frequency array, traverse in reverse direction for each digit and find the string which has the minimum characters of this type.
  • After complete reverse traversal, print the character that occurs the minimum number of times since it gives the lexicographically largest string.

Below is the implementation of the above approach.

C++

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// C++ program to find longest possible
// subsequence anagram of N strings.
#include <bits/stdc++.h>
using namespace std;
const int MAX_CHAR = 26;
  
// function to store frequency of
// each character in each string
void frequency(int fre[][MAX_CHAR], string s[], int n)
{
    for (int i = 0; i < n; i++) {
        string str = s[i];
        for (int j = 0; j < str.size(); j++) 
            fre[i][str[j] - 'a']++;        
    }
}
  
// function to Find longest possible sequence of N
// strings which is anagram to each other
void LongestSequence(int fre[][MAX_CHAR], int n)
{
    // to get lexicographical largest sequence.
    for (int i = MAX_CHAR-1; i >= 0; i--) {
  
        // find minimum of that character
        int mi = fre[0][i];
        for (int j = 1; j < n; j++) 
            mi = min(fre[j][i], mi);        
  
        // print that character
        // minimum number of times
        while (mi--) 
            cout << (char)('a' + i);        
    }
}
  
// Driver code
int main()
{
  
    string s[] = { "loo", "lol", "olive" };
    int n = sizeof(s)/sizeof(s[0]);
  
    // to strore frequency of each character in each string
    int fre[n][26] = { 0 };
  
    // to get frequency of each character
    frequency(fre, s, n);
  
    // function call
    LongestSequence(fre, n);
  
    return 0;
}

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Java














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// Java program to find longest 


// possible subsequence anagram 


// of N strings. 


class GFG 


{  


final int MAX_CHAR = 26; 


  


// function to store frequency  


// of each character in each  


// string 


static void frequency(int fre[][], 


                      String s[], int n) 


{ 


    for (int i = 0; i < n; i++)  


    { 


        String str = s[i]; 


        for (int j = 0; 


                 j < str.length(); j++)  


            fre[i][str.charAt(j) - 'a']++;      


    } 


} 


  


// function to Find longest  


// possible sequence of N 


// strings which is anagram  


// to each other 


static void LongestSequence(int fre[][],  


                            int n) 


{ 


    // to get lexicographical  


    // largest sequence. 


    for (int i = 24; i >= 0; i--) 


    { 


  


        // find minimum of 


        // that character 


        int mi = fre[0][i]; 


        for (int j = 1; j < n; j++)  


            mi = Math.min(fre[j][i], mi);      


  


        // print that character 


        // minimum number of times 


        while (mi--!=0)  


            System.out.print((char)('a' + i));      


    } 


} 


  


// Driver code 


public static void main(String args[]) 


{ 


  


    String s[] = { "loo", "lol", "olive" }; 


    int n = s.length; 


  


    // to strore frequency of each 


    // character in each string 


    int fre[][] = new int[n][26] ; 


  


    // to get frequency  


    // of each character 


    frequency(fre, s, n); 


  


    // function call 


    LongestSequence(fre, n); 


} 


} 


  


// This code is contributed 


// by Arnab Kundu 



















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Python3





# Python3 program to find longest possible

# subsequence anagram of N strings. 


# Function to store frequency of

# each character in each string

def frequency(fre, s, n): 


	for i in range(0, n):

		string = s[i]

		for j in range(0, len(string)):

			fre[i][ord(string[j]) – ord(‘a’)] += 1		


# Function to Find longest possible sequence

# of N strings which is anagram to each other

def LongestSequence(fre, n): 


	# to get lexicographical largest sequence.

	for i in range(MAX_CHAR-1, -1, -1): 


		# find minimum of that character

		mi = fre[0][i]

		for j in range(1, n):

			mi = min(fre[j][i], mi)		 


		# print that character

		# minimum number of times

		while mi:

			print(chr(ord(‘a’) + i), end = “”)

			mi -= 1


# Driver code

if __name__ == “__main__”:


	s = [“loo”, “lol”, “olive”]

	n = len(s)

	MAX_CHAR = 26


	# to strore frequency of each

	# character in each string

	fre = [[0 for i in range(26)]

	          for j in range(n)] 


	# To get frequency of each character

	frequency(fre, s, n) 


	# Function call

	LongestSequence(fre, n) 


# This code is contributed by

# Rituraj Jain



C#














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// c# program to find longest  


// possible subsequence anagram  


// of N strings.  


using System; 


  


class GFG 


{ 


public readonly int MAX_CHAR = 26; 


  


// function to store frequency  


// of each character in each  


// string  


public static void frequency(int[,] fre,  


                             string[] s, int n) 


{ 


    for (int i = 0; i < n; i++) 


    { 


        string str = s[i]; 


        for (int j = 0;  


                 j < str.Length; j++) 


        { 


            fre[i, str[j] - 'a']++; 


        } 


    } 


} 


  


// function to Find longest  


// possible sequence of N  


// strings which is anagram  


// to each other  


public static void LongestSequence(int[, ] fre,  


                                   int n) 


{ 


    // to get lexicographical  


    // largest sequence.  


    for (int i = 24; i >= 0; i--) 


    { 


  


        // find minimum of  


        // that character  


        int mi = fre[0, i]; 


        for (int j = 1; j < n; j++) 


        { 


            mi = Math.Min(fre[j, i], mi); 


        } 


  


        // print that character  


        // minimum number of times  


        while (mi--!=0) 


        { 


            Console.Write((char)('a' + i)); 


        } 


    } 


} 


  


// Driver code  


public static void Main(string[] args) 


{ 


  


    string[] s = new string[] {"loo", "lol", "olive"}; 


    int n = s.Length; 


  


    // to strore frequency of each  


    // character in each string  


    int[, ] fre = new int[n, 26]; 


  


    // to get frequency  


    // of each character  


    frequency(fre, s, n); 


  


    // function call  


    LongestSequence(fre, n); 


} 


} 


  


// This code is contributed by Shrikanth13 



















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Output:


ol






          
          
          
          

            

    

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