Longest Common Substring in an Array of Strings Last Updated : 28 Nov, 2024 Comments Improve Suggest changes Like Article Like Report We are given a list of words sharing a common stem i.e the words originate from same word for ex: the words sadness, sadly and sad all originate from the stem 'sad'. Our task is to find and return the Longest Common Substring also known as stem of those words. In case there are ties, we choose the smallest one in alphabetical order. Examples: Input : grace graceful disgraceful gracefullyOutput : graceInput : sadness sad sadlyOutput : sadThe idea is to take any word from the list as reference and form all its substrings and iterate over the entire list checking if the generated substring occurs in all of them.Below is the implementation of the above idea: C++ // C++ program to find the stem of given list of // words #include <bits/stdc++.h> using namespace std; // function to find the stem (longest common // substring) from the string array string findstem(vector<string> arr) { // Determine size of the array int n = arr.size(); // Take first word from array as reference string s = arr[0]; int len = s.length(); string res = ""; for (int i = 0; i < len; i++) { for (int j = i + 1; j <= len; j++) { // generating all possible substrings // of our reference string arr[0] i.e s string stem = s.substr(i, j); int k = 1; for (k = 1; k < n; k++) { // Check if the generated stem is // common to all words if (arr[k].find(stem) == std::string::npos) break; } // If current substring is present in // all strings and its length is greater // than current result if (k == n && res.length() < stem.length()) res = stem; } } return res; } // Driver code int main() { vector<string> arr{ "grace", "graceful", "disgraceful", "gracefully" }; // Function call string stems = findstem(arr); cout << stems << endl; } // This code is contributed by // sanjeev2552 Java // Java program to find the stem of given list of // words import java.io.*; import java.util.*; class stem { // function to find the stem (longest common // substring) from the string array public static String findstem(String arr[]) { // Determine size of the array int n = arr.length; // Take first word from array as reference String s = arr[0]; int len = s.length(); String res = ""; for (int i = 0; i < len; i++) { for (int j = i + 1; j <= len; j++) { // generating all possible substrings // of our reference string arr[0] i.e s String stem = s.substring(i, j); int k = 1; for (k = 1; k < n; k++) // Check if the generated stem is // common to all words if (!arr[k].contains(stem)) break; // If current substring is present in // all strings and its length is greater // than current result if (k == n && res.length() < stem.length()) res = stem; } } return res; } // Driver Code public static void main(String args[]) { String arr[] = { "grace", "graceful", "disgraceful","gracefully" }; // Function call String stems = findstem(arr); System.out.println(stems); } } Python # Python 3 program to find the stem # of given list of words # function to find the stem (longest # common substring) from the string array def findstem(arr): # Determine size of the array n = len(arr) # Take first word from array # as reference s = arr[0] l = len(s) res = "" for i in range(l): for j in range(i + 1, l + 1): # generating all possible substrings # of our reference string arr[0] i.e s stem = s[i:j] k = 1 for k in range(1, n): # Check if the generated stem is # common to all words if stem not in arr[k]: break # If current substring is present in # all strings and its length is greater # than current result if (k + 1 == n and len(res) < len(stem)): res = stem return res # Driver Code if __name__ == "__main__": arr = ["grace", "graceful", "disgraceful", "gracefully"] # Function call stems = findstem(arr) print(stems) # This code is contributed by ita_c C# // C# program to find the stem of given list of // words using System; using System.Collections.Generic; class stem { // function to find the stem (longest common // substring) from the string array public static String findstem(String []arr) { // Determine size of the array int n = arr.Length; // Take first word from array as reference String s = arr[0]; int len = s.Length; String res = ""; for (int i = 0; i < len; i++) { for (int j = i + 1; j <= len; j++) { // generating all possible substrings // of our reference string arr[0] i.e s String stem = s.Substring(i, j-i); int k = 1; for (k = 1; k < n; k++) // Check if the generated stem is // common to all words if (!arr[k].Contains(stem)) break; // If current substring is present in // all strings and its length is greater // than current result if (k == n && res.Length < stem.Length) res = stem; } } return res; } // Driver Code public static void Main(String []args) { String []arr = { "grace", "graceful", "disgraceful", "gracefully" }; // Function call String stems = findstem(arr); Console.WriteLine(stems); } } // This code contributed by Rajput-Ji JavaScript // JavaScript program to find the stem of given list of // words function findstem(arr) { // Determine size of the array let n = arr.length; // Take first word from array as reference let s = arr[0]; let len = s.length; let res = ""; for (let i = 0; i < len; i++) { for (let j = i + 1; j <= len; j++) { // generating all possible substrings // of our reference string arr[0] i.e s let stem = s.substring(i, j); let k = 1; for (k = 1; k < n; k++) { // Check if the generated stem is // common to all words if (!arr[k].includes(stem)) break; } // If current substring is present in // all strings and its length is greater // than current result if (k === n && res.length < stem.length) res = stem; } } return res; } // Driver Code let arr = ["grace", "graceful", "disgraceful", "gracefully"]; // Function call let stems = findstem(arr); console.log(stems); PHP <?php // PHP program to find the stem of given list of // words // function to find the stem (longest common // substring) from the string array function findstem($arr) { // Determine size of the array $n = count($arr); // Take first word from array as reference $s = $arr[0]; $len = strlen($s); $res = ""; for ($i = 0; $i < $len; $i++) { for ($j = $i+1; $j <=$len; $j++) { // generating all possible substrings // of our reference string arr[0] i.e s $stem = substr($s,$i, $j-$i); $k = 1; for ($k = 1; $k < $n; $k++) // Check if the generated stem is // common to all words if (!strpos($arr[$k],$stem)) break; // If current substring is present in // all strings and its length is greater // than current result if ($k <= $n && strlen($res) < strlen($stem)) $res = $stem; } } return $res; } // Driver Code $arr = array( "grace", "graceful", "disgraceful", "gracefully" ); // Function call $stems = findstem($arr); print($stems); // This code is contributed by mits ?> Outputgrace Time Complexity: O(L2 * n * m) Auxiliary Space: O(L). 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