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

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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++

// 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; 
} 

Java

// 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 

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#

// 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 

Output:

ol

My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Java

Python3

C#

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