# Count different numbers possible using all the digits their frequency times

• Last Updated : 02 May, 2019

Given an array arr[] which contains the frequency of the digits (0-9), the task is to find the count of numbers possible using each digit its frequency times. That is, the final numbers generated should contain all of the digits their frequency times. Since, the count can be very large return the answer modulo 10^9+7.

Prerequisites: Factorial of a number, Modular multiplicative inverse
Examples:

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.  To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.

```Input : arr[] = {0, 1, 1, 0, 0, 0, 0, 0, 0, 0}
Output : 2
Frequency of 1 and 2 is 1 and all the rest is 0.
Therefore, 2 possible numbers are 12 and 21.

Input : arr[] = {0, 5, 2, 0, 0, 0, 4, 0, 1, 1}
Output : 1081080
```

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

Approach: The problem can be easily solved using Permutation and Combinations. The ith index of array arr[] gives the frequency of ith digit. The problem can be thought of as finding the total permutation of X objects where X0 objects are of one type, X1 objects are of another type and so on. Then the possible count of numbers is given by:

Total Count = X! / (X0! * X1! *…..* X9!)

where X = Sum of frequencies of all the digits and Xi = the frequency of ith digit.

Below is the implementation of the above approach

## C++

 `// C++ implementation of the above approach`` ` `#include ``using` `namespace` `std;`` ` `#define ll long long``#define MAXN 100000``#define MOD 1000000007`` ` `// Initialize an array to store factorial values``ll fact[MAXN];`` ` `// Function to calculate and store X! values``void` `factorial()``{``    ``fact = 1;``    ``for` `(``int` `i = 1; i < MAXN; i++)``        ``fact[i] = (fact[i - 1] * i) % MOD;``}`` ` `// Iterative Function to calculate (x^y)%p in O(log y)``ll power(ll x, ll y, ll p)``{``    ``ll res = 1; ``// Initialize result`` ` `    ``x = x % p; ``// Update x if it is more than or``    ``// equal to p`` ` `    ``while` `(y > 0) {``        ``// If y is odd, multiply x with result``        ``if` `(y & 1)``            ``res = (res * x) % p;`` ` `        ``// y must be even now``        ``y = y >> 1; ``// y = y/2``        ``x = (x * x) % p;``    ``}``    ``return` `res;``}`` ` `// Function that return modular``// inverse of x under modulo p``ll modInverse(ll x, ll p)``{``    ``return` `power(x, p - 2, p);``}`` ` `// Function that returns the count of``// different number possible by using``// all the digits its frequency times``ll countDifferentNumbers(ll arr[], ll P)``{``    ``// Preprocess factorial values``    ``factorial();`` ` `    ``// Initialize the result and sum``    ``// of aint the frequencies``    ``ll res = 0, X = 0;`` ` `    ``// Calculate the sum of frequencies``    ``for` `(``int` `i = 0; i < 10; i++)``        ``X += arr[i];`` ` `    ``// Putting res equal to x!``    ``res = fact[X];`` ` `    ``// Multiplying res with modular``    ``// inverse of X0!, X1!, .., X9!``    ``for` `(``int` `i = 0; i < 10; i++) {``        ``if` `(arr[i] > 1)``            ``res = (res * modInverse(fact[arr[i]], P)) % P;``    ``}`` ` `    ``return` `res;``}`` ` `// Driver Code``int` `main()``{``    ``ll arr[] = { 1, 0, 2, 0, 0, 7, 4, 0, 0, 3 };``    ``cout << countDifferentNumbers(arr, MOD);`` ` `    ``return` `0;``}`

## Java

 `// Java program to implement``// the above approach``class` `GFG``{`` ` `static` `int` `MAXN = ``100000``;``static` `int` `MOD = ``1000000007``;`` ` `// Initialize an array to store factorial values``static` `long` `fact[] = ``new` `long``[MAXN];`` ` `// Function to calculate and store X! values``static` `void` `factorial()``{``    ``fact[``0``] = ``1``;``    ``for` `(``int` `i = ``1``; i < MAXN; i++)``        ``fact[i] = (fact[i - ``1``] * i) % MOD;``}`` ` `// Iterative Function to calculate (x^y)%p in O(log y)``static` `long` `power(``long` `x, ``long` `y, ``long` `p)``{``    ``long` `res = ``1``; ``// Initialize result`` ` `    ``x = x % p; ``// Update x if it is more than or``    ``// equal to p`` ` `    ``while` `(y > ``0``)``    ``{``        ``// If y is odd, multiply x with result``        ``if` `(y % ``2``== ``1``)``            ``res = (res * x) % p;`` ` `        ``// y must be even now``        ``y = y >> ``1``; ``// y = y/2``        ``x = (x * x) % p;``    ``}``    ``return` `res;``}`` ` `// Function that return modular``// inverse of x under modulo p``static` `long` `modInverse(``long` `x, ``long` `p)``{``    ``return` `power(x, p - ``2``, p);``}`` ` `// Function that returns the count of``// different number possible by using``// along the digits its frequency times``static` `long` `countDifferentNumbers(``long` `arr[], ``long` `P)``{``    ``// Preprocess factorial values``    ``factorial();`` ` `    ``// Initialize the result and sum``    ``// of aint the frequencies``    ``long` `res = ``0``, X = ``0``;`` ` `    ``// Calculate the sum of frequencies``    ``for` `(``int` `i = ``0``; i < ``10``; i++)``        ``X += arr[i];`` ` `    ``// Putting res equal to x!``    ``res = fact[(``int``)X];`` ` `    ``// Multiplying res with modular``    ``// inverse of X0!, X1!, .., X9!``    ``for` `(``int` `i = ``0``; i < ``10``; i++)``    ``{``        ``if` `(arr[i] > ``1``)``            ``res = (res * modInverse(fact[(``int``)arr[i]], P)) % P;``    ``}`` ` `    ``return` `res;``}`` ` `// Driver Code``public` `static` `void` `main(String[] args) ``{``    ``long` `arr[] = { ``1``, ``0``, ``2``, ``0``, ``0``, ``7``, ``4``, ``0``, ``0``, ``3` `};``    ``System.out.println(countDifferentNumbers(arr, MOD));``}``}`` ` `/* This code contributed by PrinciRaj1992 */`

## Python3

 `# Python3 implementation of the above approach ``MAXN ``=` `100000``MOD ``=` `1000000007`` ` `# Initialize an array to store``# factorial values ``fact ``=` `[``0``] ``*` `MAXN; `` ` `# Function to calculate and store X! values ``def` `factorial() :``    ``fact[``0``] ``=` `1``    ``for` `i ``in` `range``(``1``, MAXN) :``        ``fact[i] ``=` `(fact[i ``-` `1``] ``*` `i) ``%` `MOD`` ` `# Iterative Function to calculate``# (x^y)%p in O(log y) ``def` `power(x, y, p) : `` ` `    ``res ``=` `1` `# Initialize result `` ` `    ``x ``=` `x ``%` `p ``# Update x if it is more than  ``              ``# or equal to p `` ` `    ``while` `(y > ``0``) :``         ` `        ``# If y is odd, multiply x with result ``        ``if` `(y & ``1``) :``            ``res ``=` `(res ``*` `x) ``%` `p `` ` `        ``# y must be even now ``        ``y ``=` `y >> ``1``; ``# y = y/2 ``        ``x ``=` `(x ``*` `x) ``%` `p``     ` `    ``return` `res`` ` `# Function that return modular ``# inverse of x under modulo p ``def` `modInverse(x, p) : ``    ``return` `power(x, p ``-` `2``, p) `` ` `# Function that returns the count of ``# different number possible by using ``# all the digits its frequency times ``def` `countDifferentNumbers(arr, P) : `` ` `    ``# Preprocess factorial values ``    ``factorial(); `` ` `    ``# Initialize the result and sum ``    ``# of aint the frequencies ``    ``res ``=` `0``; X ``=` `0``; `` ` `    ``# Calculate the sum of frequencies ``    ``for` `i ``in` `range``(``10``) :``        ``X ``+``=` `arr[i] `` ` `    ``# Putting res equal to x! ``    ``res ``=` `fact[X] `` ` `    ``# Multiplying res with modular ``    ``# inverse of X0!, X1!, .., X9! ``    ``for` `i ``in` `range``(``10``) :``        ``if` `(arr[i] > ``1``) :``            ``res ``=` `(res ``*` `modInverse(fact[arr[i]], P)) ``%` `P; `` ` `    ``return` `res; `` ` `# Driver Code ``if` `__name__ ``=``=` `"__main__"` `: `` ` `    ``arr ``=` `[``1``, ``0``, ``2``, ``0``, ``0``, ``7``, ``4``, ``0``, ``0``, ``3` `]``    ``print``(countDifferentNumbers(arr, MOD)) ``     ` `# This code is contributed by Ryuga`

## C#

 `// C# program to implement``// the above approach``using` `System;`` ` `class` `GFG``{`` ` `    ``static` `int` `MAXN = 100000;``    ``static` `int` `MOD = 1000000007;``     ` `    ``// Initialize an array to store factorial values``    ``static` `long` `[]fact = ``new` `long``[MAXN];``     ` `    ``// Function to calculate and store X! values``    ``static` `void` `factorial()``    ``{``        ``fact = 1;``        ``for` `(``int` `i = 1; i < MAXN; i++)``            ``fact[i] = (fact[i - 1] * i) % MOD;``    ``}``     ` `    ``// Iterative Function to calculate (x^y)%p in O(log y)``    ``static` `long` `power(``long` `x, ``long` `y, ``long` `p)``    ``{``        ``long` `res = 1; ``// Initialize result``     ` `        ``x = x % p; ``// Update x if it is more than or``        ``// equal to p``     ` `        ``while` `(y > 0)``        ``{``            ``// If y is odd, multiply x with result``            ``if` `(y % 2== 1)``                ``res = (res * x) % p;``     ` `            ``// y must be even now``            ``y = y >> 1; ``// y = y/2``            ``x = (x * x) % p;``        ``}``        ``return` `res;``    ``}``     ` `    ``// Function that return modular``    ``// inverse of x under modulo p``    ``static` `long` `modInverse(``long` `x, ``long` `p)``    ``{``        ``return` `power(x, p - 2, p);``    ``}``     ` `    ``// Function that returns the count of``    ``// different number possible by using``    ``// along the digits its frequency times``    ``static` `long` `countDifferentNumbers(``long` `[]arr, ``long` `P)``    ``{``        ``// Preprocess factorial values``        ``factorial();``     ` `        ``// Initialize the result and sum``        ``// of aint the frequencies``        ``long` `res = 0, X = 0;``     ` `        ``// Calculate the sum of frequencies``        ``for` `(``int` `i = 0; i < 10; i++)``            ``X += arr[i];``     ` `        ``// Putting res equal to x!``        ``res = fact[(``int``)X];``     ` `        ``// Multiplying res with modular``        ``// inverse of X0!, X1!, .., X9!``        ``for` `(``int` `i = 0; i < 10; i++)``        ``{``            ``if` `(arr[i] > 1)``                ``res = (res * modInverse(fact[(``int``)arr[i]], P)) % P;``        ``}``     ` `        ``return` `res;``    ``}``     ` `    ``// Driver Code``    ``public` `static` `void` `Main(String[] args) ``    ``{``        ``long` `[]arr = { 1, 0, 2, 0, 0, 7, 4, 0, 0, 3 };``        ``Console.WriteLine(countDifferentNumbers(arr, MOD));``    ``}``}`` ` `// This code has been contributed by 29AjayKumar`
Output:
```245044800
```

My Personal Notes arrow_drop_up