 Open in App
Not now

# Count of distinct groups of strings formed after performing equivalent operation

• Difficulty Level : Medium
• Last Updated : 29 May, 2022

Given an array arr[] of N strings consisting of lowercase alphabets, the task is to find the number of distinct groups of strings formed after performing the equivalent operation.

Two strings are said to be equivalent if there exists the same character in both the strings and if there exists another string that is equivalent to one of the strings in the group of equivalent string then that string is also equivalent to that group.

Examples:

Input: arr[] = {“a”, “b”, “ab”, “d”}
Output: 2
Explanation:
As strings “b” and “ab” have ‘b’ as the same character, they are equivalent also “ab” and  the string”a” have ‘a’ as the same character, so the strings “a”, “b”, “ab” are equivalent and “d” is another string.

Therefore, the count of distinct group of strings formed is 2.

Input: arr[] = {“ab”, “bc”, “abc”}
Output: 1

Approach: The given problem can be solved using the Disjoint Set Union, the idea is to traverse the string and mark all the characters of the current string as true and perform the union operation on the first character of the current string with the character ‘a’, and count the different number of parents in the parent vector and store it. Follow the below steps to solve the problem:

• Initialize the vectors parent(27), rank(27, 0), total(26, false), and current(26, false).
• Initialize a variable, say distCount as 0 that stores the count of distinct strings.
• Iterate over the range [0, 27) using the variable i and set the value of parent[i] as i.
• Iterate over the range [0, N) using the variable i and perform the following steps:
• Iterate over the range [0, 26) using the variable j and set current[j] to false.
• Iterate over the characters of the string arr[i] using the variable ch and set current[ch – ‘a’] to true.
• Iterate over the range [0, 26) using the variable j and if current[j] is true then set total[j] to true and call for the function Union(parent, rank, arr[i] – ‘a’, j).
• Iterate over the range [0, 26) using the variable i and check if total[i] is true and Find(parent, i) is I if it is true then increment the value of distCount by 1.
• Finally, print the value of distCount.

Below is the implementation of the above approach:

## C++

 `// C++ program for the above approach``#include ``using` `namespace` `std;` `// Function to perform the find operation``// to find the parent of a disjoint set``int` `Find(vector<``int``>& parent, ``int` `a)``{``    ``return` `parent[a]``           ``= (parent[a] == a ? a : Find(parent, parent[a]));``}` `// Function to perform union operation``// of disjoint set union``void` `Union(vector<``int``>& parent,``           ``vector<``int``>& rank, ``int` `a,``           ``int` `b)``{` `    ``// Find the parent of node a and b``    ``a = Find(parent, a);``    ``b = Find(parent, b);` `    ``// Update the rank``    ``if` `(rank[a] == rank[b])``        ``rank[a]++;``    ``if` `(rank[a] > rank[b])``        ``parent[b] = a;``    ``else``        ``parent[a] = b;``}` `// Function to find the number of distinct``// strings after performing the``// given operations``void` `numOfDistinctStrings(string arr[],``                          ``int` `N)``{``    ``// Stores the parent elements``    ``// of the sets``    ``vector<``int``> parent(27);` `    ``// Stores the rank of the sets``    ``vector<``int``> rank(27, 0);` `    ``for` `(``int` `j = 0; j < 27; j++) {``        ``// Update parent[i] to i``        ``parent[j] = j;``    ``}` `    ``// Stores the total characters``    ``// traversed through the strings``    ``vector<``bool``> total(26, ``false``);` `    ``// Stores the current characters``    ``// traversed through a string``    ``vector<``bool``> current(26, ``false``);` `    ``for` `(``int` `i = 0; i < N; i++) {` `        ``for` `(``int` `j = 0; j < 26; j++) {` `            ``// Update current[i] to false``            ``current[j] = ``false``;``        ``}` `        ``for` `(``char` `ch : arr[i]) {` `            ``// Update current[ch - 'a'] to true``            ``current[ch - ``'a'``] = ``true``;``        ``}` `        ``for` `(``int` `j = 0; j < 26; j++) {` `            ``// Check if current[j] is true``            ``if` `(current[j]) {` `                ``// Update total[j] to true``                ``total[j] = ``true``;` `                ``// Add arr[i] - 'a' and``                ``// j elements to same set``                ``Union(parent, rank,``                      ``arr[i] - ``'a'``, j);``            ``}``        ``}``    ``}` `    ``// Stores the count of distinct strings``    ``int` `distCount = 0;``    ``for` `(``int` `i = 0; i < 26; i++) {` `        ``// Check total[i] is true and``        ``// parent of i is i only``        ``if` `(total[i] && Find(parent, i) == i) {` `            ``// Increment the value of``            ``// distCount by 1``            ``distCount++;``        ``}``    ``}` `    ``// Print the value of distCount``    ``cout << distCount << endl;``}` `// Driver Code``int` `main()``{``    ``string arr[] = { ``"a"``, ``"ab"``, ``"b"``, ``"d"` `};``    ``int` `N = ``sizeof``(arr) / ``sizeof``(arr);``    ``numOfDistinctStrings(arr, N);` `    ``return` `0;``}`

## Python3

 `# python program for the above approach` `# Function to perform the find operation``# to find the parent of a disjoint set``def` `Find(parent, a):``    ``if` `parent[a] ``=``=` `a:``        ``parent[a] ``=` `a``        ``return` `parent[a]``    ``else``:``        ``parent[a] ``=` `Find(parent, parent[a])``        ``return` `parent[a]` `# Function to perform union operation``# of disjoint set union``def` `Union(parent, rank, a, b):` `        ``# Find the parent of node a and b``    ``a ``=` `Find(parent, a)``    ``b ``=` `Find(parent, b)` `    ``# Update the rank``    ``if` `(rank[a] ``=``=` `rank[b]):``        ``rank[a] ``+``=` `1``    ``if` `(rank[a] > rank[b]):``        ``parent[b] ``=` `a``    ``else``:``        ``parent[a] ``=` `b` `# Function to find the number of distinct``# strings after performing the``# given operations``def` `numOfDistinctStrings(arr, N):` `    ``# Stores the parent elements``    ``# of the sets``    ``parent ``=` `[``0` `for` `_ ``in` `range``(``27``)]` `    ``# Stores the rank of the sets``    ``rank ``=` `[``0` `for` `_ ``in` `range``(``27``)]` `    ``for` `j ``in` `range``(``0``, ``27``):``        ``# Update parent[i] to i``        ``parent[j] ``=` `j` `    ``# Stores the total characters``    ``# traversed through the strings``    ``total ``=` `[``False` `for` `_ ``in` `range``(``26``)]` `    ``# Stores the current characters``    ``# traversed through a string``    ``current ``=` `[``False` `for` `_ ``in` `range``(``26``)]` `    ``for` `i ``in` `range``(``0``, N):` `        ``for` `j ``in` `range``(``0``, ``26``):` `            ``# Update current[i] to false``            ``current[j] ``=` `False` `        ``for` `ch ``in` `arr[i]:` `            ``# Update current[ch - 'a'] to true``            ``current[``ord``(ch) ``-` `ord``(``'a'``)] ``=` `True` `        ``for` `j ``in` `range``(``0``, ``26``):` `            ``# Check if current[j] is true``            ``if` `(current[j]):` `                ``# Update total[j] to true``                ``total[j] ``=` `True` `                ``# Add arr[i] - 'a' and``                ``# j elements to same set``                ``Union(parent, rank, ``ord``(arr[i][``0``]) ``-` `ord``(``'a'``), j)` `    ``# Stores the count of distinct strings``    ``distCount ``=` `0``    ``for` `i ``in` `range``(``0``, ``26``):` `        ``# Check total[i] is true and``        ``# parent of i is i only``        ``if` `(total[i] ``and` `Find(parent, i) ``=``=` `i):` `            ``# Increment the value of``            ``# distCount by 1``            ``distCount ``+``=` `1` `    ``# Print the value of distCount``    ``print``(distCount)` `# Driver Code``if` `__name__ ``=``=` `"__main__"``:` `    ``arr ``=` `[``"a"``, ``"ab"``, ``"b"``, ``"d"``]``    ``N ``=` `len``(arr)``    ``numOfDistinctStrings(arr, N)` `    ``# This code is contributed by rakeshsahni`

## C#

 `// C# program for the above approach``using` `System;``class` `GFG {` `    ``// Function to perform the find operation``    ``// to find the parent of a disjoint set``    ``static` `int` `Find(``int``[] parent, ``int` `a)``    ``{``        ``return` `parent[a]``            ``= (parent[a] == a ? a``                              ``: Find(parent, parent[a]));``    ``}` `    ``// Function to perform union operation``    ``// of disjoint set union``    ``static` `void` `Union(``int``[] parent, ``int``[] rank, ``int` `a,``                      ``int` `b)``    ``{` `        ``// Find the parent of node a and b``        ``a = Find(parent, a);``        ``b = Find(parent, b);` `        ``// Update the rank``        ``if` `(rank[a] == rank[b])``            ``rank[a]++;``        ``if` `(rank[a] > rank[b])``            ``parent[b] = a;``        ``else``            ``parent[a] = b;``    ``}` `    ``// Function to find the number of distinct``    ``// strings after performing the``    ``// given operations``    ``static` `void` `numOfDistinctStrings(``string``[] arr, ``int` `N)``    ``{``        ``// Stores the parent elements``        ``// of the sets``        ``int``[] parent = ``new` `int``[(27)];` `        ``// Stores the rank of the sets``        ``int``[] rank = ``new` `int``[(27)];` `        ``for` `(``int` `j = 0; j < 27; j++) {``            ``// Update parent[i] to i``            ``parent[j] = j;``        ``}` `        ``// Stores the total characters``        ``// traversed through the strings``        ``bool``[] total = ``new` `bool``;` `        ``// Stores the current characters``        ``// traversed through a string``        ``bool``[] current = ``new` `bool``;` `        ``for` `(``int` `i = 0; i < N; i++) {` `            ``for` `(``int` `j = 0; j < 26; j++) {` `                ``// Update current[i] to false``                ``current[j] = ``false``;``            ``}` `            ``foreach``(``char` `ch ``in` `arr[i])``            ``{` `                ``// Update current[ch - 'a'] to true``                ``current[ch - ``'a'``] = ``true``;``            ``}` `            ``for` `(``int` `j = 0; j < 26; j++) {` `                ``// Check if current[j] is true``                ``if` `(current[j]) {` `                    ``// Update total[j] to true``                    ``total[j] = ``true``;` `                    ``// Add arr[i] - 'a' and``                    ``// j elements to same set``                    ``Union(parent, rank, arr[i] - ``'a'``, j);``                ``}``            ``}``        ``}` `        ``// Stores the count of distinct strings``        ``int` `distCount = 0;``        ``for` `(``int` `i = 0; i < 26; i++) {` `            ``// Check total[i] is true and``            ``// parent of i is i only``            ``if` `(total[i] && Find(parent, i) == i) {` `                ``// Increment the value of``                ``// distCount by 1``                ``distCount++;``            ``}``        ``}` `        ``// Print the value of distCount``        ``Console.WriteLine(distCount);``    ``}` `    ``// Driver Code``    ``public` `static` `void` `Main()``    ``{``        ``string``[] arr = { ``"a"``, ``"ab"``, ``"b"``, ``"d"` `};``        ``int` `N = arr.Length;``        ``numOfDistinctStrings(arr, N);``    ``}``}` `// This code is contributed by ukasp.`

Output:

`2`

Time Complexity: O(N*log N), as we are using a loop to traverse N times and Union function will cost us logN time.
Auxiliary Space: O(1), as we are using a constant space of size 27.

My Personal Notes arrow_drop_up