# Find the number of strings formed using distinct characters of a given string

• Difficulty Level : Hard
• Last Updated : 15 Mar, 2021

Given a string str consisting of lowercase English alphabets, the task is to find the count of all possible string of maximum length that can be formed using the characters of str such that no two characters in the generated string are same.
Examples:

Input: str = “aba”
Output:
“ab” and “ba” are the only valid strings.
Input: str = “geeksforgeeks”
Output: 5040

Approach: First, count the number of distinct characters in the string say cnt as no two characters can be same in the resultant string. Now, the total number of strings that can be formed with cnt number of characters is cnt! as every character of str has to be present in the generated string in order to maximise the length and no character should appear more than once.
Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach` `#include ` `using` `namespace` `std;`   `// Function to return the factorial of n` `int` `fact(``int` `n)` `{` `    ``int` `fact = 1;` `    ``for` `(``int` `i = 1; i <= n; i++)` `        ``fact *= i;`   `    ``return` `fact;` `}`   `// Function to return the count of all` `// possible strings that can be formed` `// with the characters of the given string` `// without repeating characters` `int` `countStrings(string str, ``int` `n)` `{`   `    ``// To store the distinct characters` `    ``// of the string str` `    ``set<``char``> distinct_char;` `    ``for` `(``int` `i = 0; i < n; i++) {` `        ``distinct_char.insert(str[i]);` `    ``}`   `    ``return` `fact(distinct_char.size());` `}`   `// Driver code` `int` `main()` `{` `    ``string str = ``"geeksforgeeks"``;` `    ``int` `n = str.length();`   `    ``cout << countStrings(str, n);`   `    ``return` `0;` `}`

## Java

 `// Java implementation of the approach ` `import` `java.util.*;`   `class` `GFG ` `{`   `// Function to return the factorial of n` `static` `int` `fact(``int` `n)` `{` `    ``int` `fact = ``1``;` `    ``for` `(``int` `i = ``1``; i <= n; i++)` `        ``fact *= i;`   `    ``return` `fact;` `}`   `// Function to return the count of all` `// possible strings that can be formed` `// with the characters of the given string` `// without repeating characters` `static` `int` `countStrings(String str, ``int` `n)` `{`   `    ``// To store the distinct characters` `    ``// of the string str` `    ``Set distinct_char = ``new` `HashSet<>();` `    ``for` `(``int` `i = ``0``; i < n; i++) ` `    ``{` `        ``distinct_char.add(str.charAt(i));` `    ``}`   `    ``return` `fact(distinct_char.size());` `}`   `// Driver code` `public` `static` `void` `main(String[] args)` `{` `    ``String str = ``"geeksforgeeks"``;` `    ``int` `n = str.length();`   `    ``System.out.println(countStrings(str, n));` `}` `}`   `// This code is contributed by PrinciRaj1992`

## Python3

 `# Python3 implementation of the approach `   `# Function to return the factorial of n ` `def` `fact(n) : `   `    ``fact ``=` `1``; ` `    ``for` `i ``in` `range``(``1``, n ``+` `1``) :` `        ``fact ``*``=` `i; `   `    ``return` `fact; `   `# Function to return the count of all ` `# possible strings that can be formed ` `# with the characters of the given string ` `# without repeating characters ` `def` `countStrings(string, n) : `   `    ``# To store the distinct characters ` `    ``# of the string str ` `    ``distinct_char ``=` `set``(); ` `    ``for` `i ``in` `range``(n) : ` `        ``distinct_char.add(string[i]); ` `    `  `    ``return` `fact(``len``(distinct_char)); `   `# Driver code ` `if` `__name__ ``=``=` `"__main__"` `: `   `    ``string ``=` `"geeksforgeeks"``; ` `    ``n ``=` `len``(string); `   `    ``print``(countStrings(string, n)); `   `# This code is contributed by AnkitRai01`

## C#

 `// C# implementation of the approach` `using` `System;` `using` `System.Collections.Generic;`   `class` `GFG ` `{`   `// Function to return the factorial of n` `static` `int` `fact(``int` `n)` `{` `    ``int` `fact = 1;` `    ``for` `(``int` `i = 1; i <= n; i++)` `        ``fact *= i;`   `    ``return` `fact;` `}`   `// Function to return the count of all` `// possible strings that can be formed` `// with the characters of the given string` `// without repeating characters` `static` `int` `countStrings(String str, ``int` `n)` `{`   `    ``// To store the distinct characters` `    ``// of the string str` `    ``HashSet<``char``> distinct_char = ``new` `HashSet<``char``>();` `    ``for` `(``int` `i = 0; i < n; i++) ` `    ``{` `        ``distinct_char.Add(str[i]);` `    ``}`   `    ``return` `fact(distinct_char.Count);` `}`   `// Driver code` `public` `static` `void` `Main(String[] args)` `{` `    ``String str = ``"geeksforgeeks"``;` `    ``int` `n = str.Length;`   `    ``Console.WriteLine(countStrings(str, n));` `}` `}`   `// This code is contributed by 29AjayKumar`

## Javascript

 ``

Output:

`5040`

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