# Finding powers of any number P in N!

• Last Updated : 11 Sep, 2021

Prerequisite: Print all prime factors and their powers
Given natural numbers N and P, the task is to find the power of P in the factorization of N!.

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: N = 4, P = 2
Output:
Explanation:
Power of 2 in the prime factorization of 4! = 24 is 3

Input: N = 24, P = 4
Output: 11

Naive Approach: The idea is to find the power of P for each number from 1 to N and add them as we know during multiplication power is added.

Time Complexity: O(N*P)

Efficient Approach:
To find the power of the number P in N! do the following:

1. Find all the Prime Factors of the number P with their frequency by using the approach discussed in this article. Store the Prime Factors with their frequency in the map.
2. Find the power of every Prime Factors of P in the factorization of N! by using the approach discussed in this article.
3. Divide every power obtained in the above steps by their corresponding frequency in the map.
4. Store the result of the above steps in an array, and a minimum of those elements will give the power of P in the factorization of N!.

Below is the implementation of the above approach:

## C++

 `// C++ program to find the power``// of P in N!``#include ``using` `namespace` `std;` `// Map to store all the prime``// factors of P``unordered_map<``int``, ``int``> Map;` `// Function to find the prime``// factors of N im Map``void` `findPrimeFactors(``int` `N)``{``    ``int` `i;` `    ``// Clear map``    ``Map.clear();` `    ``// Check for factors of 2``    ``while` `(N % 2 == 0) {``        ``Map += 1;``        ``N /= 2;``    ``}` `    ``// Find all the prime factors``    ``for` `(i = 3; i <= ``sqrt``(N); i += 2) {` `        ``// If i is a factors``        ``// then increase the``        ``// frequency of i``        ``while` `(N % i == 0) {``            ``Map[i] += 1;``            ``N /= i;``        ``}``    ``}` `    ``if` `(N > 2) {``        ``Map[N] += 1;``    ``}``}` `// Function to find the power``// of prime number P in N!``int` `PowInFactN(``int` `N, ``int` `P)``{``    ``int` `ans = 0;``    ``int` `temp = P;` `    ``// Loop until temp <= N``    ``while` `(temp <= N) {` `        ``// Add the number of``        ``// numbers divisible``        ``// by N``        ``ans += N / temp;` `        ``// Each time multiply``        ``// temp by P``        ``temp = temp * P;``    ``}` `    ``// Returns ans``    ``return` `ans;``}` `// Function that find the``// powers of any P in N!``int` `findPowers(``int` `N, ``int` `P)``{` `    ``// Find all prime factors``    ``// of number P``    ``findPrimeFactors(P);` `    ``// To store the powers of``    ``// all prime factors``    ``vector<``int``> Powers;` `    ``// Traverse the map``    ``for` `(``auto``& it : Map) {` `        ``// Prime factor and``        ``// corres. powers``        ``int` `primeFac = it.first;``        ``int` `facPow = it.second;` `        ``// Find power of prime``        ``// factor primeFac``        ``int` `p = PowInFactN(N,``                           ``primeFac);` `        ``// Divide frequency by``        ``// facPow``        ``p /= facPow;` `        ``// Store the power of``        ``// primeFac^facPow``        ``Powers.push_back(p);``    ``}` `    ``// Return the minimum``    ``// element in Power array``    ``return` `*min_element(Powers.begin(),``                        ``Powers.end());``}` `// Driver's Code``int` `main()``{``    ``int` `N = 24, P = 4;` `    ``// Function to find power of``    ``// P in N!``    ``cout << findPowers(N, P);``    ``return` `0;``}`

## Java

 `// Java program to find the power``// of P in N!``import` `java.util.*;` `class` `GFG{`` ` `// Map to store all the prime``// factors of P``static` `HashMap Map = ``new` `HashMap();`` ` `// Function to find the prime``// factors of N im Map``static` `void` `findPrimeFactors(``int` `N)``{``    ``int` `i;`` ` `    ``// Clear map``    ``Map.clear();`` ` `    ``// Check for factors of 2``    ``while` `(N % ``2` `== ``0``) {``        ``if``(Map.containsKey(``2``))``            ``Map.put(``2``, Map.get(``2``) + ``1``);``        ``else``            ``Map.put(``2``, ``1``);``        ``N /= ``2``;``    ``}`` ` `    ``// Find all the prime factors``    ``for` `(i = ``3``; i <= Math.sqrt(N); i += ``2``) {`` ` `        ``// If i is a factors``        ``// then increase the``        ``// frequency of i``        ``while` `(N % i == ``0``) {``            ``if``(Map.containsKey(i))``                ``Map.put(i, Map.get(i) + ``1``);``            ``else``                ``Map.put(i, ``1``);``            ``N /= i;``        ``}``    ``}`` ` `    ``if` `(N > ``2``) {``        ``if``(Map.containsKey(N))``            ``Map.put(N, Map.get(N) + ``1``);``        ``else``            ``Map.put(N, ``1``);``    ``}``}`` ` `// Function to find the power``// of prime number P in N!``static` `int` `PowInFactN(``int` `N, ``int` `P)``{``    ``int` `ans = ``0``;``    ``int` `temp = P;`` ` `    ``// Loop until temp <= N``    ``while` `(temp <= N) {`` ` `        ``// Add the number of``        ``// numbers divisible``        ``// by N``        ``ans += N / temp;`` ` `        ``// Each time multiply``        ``// temp by P``        ``temp = temp * P;``    ``}`` ` `    ``// Returns ans``    ``return` `ans;``}`` ` `// Function that find the``// powers of any P in N!``static` `int` `findPowers(``int` `N, ``int` `P)``{`` ` `    ``// Find all prime factors``    ``// of number P``    ``findPrimeFactors(P);`` ` `    ``// To store the powers of``    ``// all prime factors``    ``Vector Powers = ``new` `Vector();`` ` `    ``// Traverse the map``    ``for` `(Map.Entry it : Map.entrySet()) {`` ` `        ``// Prime factor and``        ``// corres. powers``        ``int` `primeFac = it.getKey();``        ``int` `facPow = it.getValue();`` ` `        ``// Find power of prime``        ``// factor primeFac``        ``int` `p = PowInFactN(N,``                           ``primeFac);`` ` `        ``// Divide frequency by``        ``// facPow``        ``p /= facPow;`` ` `        ``// Store the power of``        ``// primeFac^facPow``        ``Powers.add(p);``    ``}`` ` `    ``// Return the minimum``    ``// element in Power array``    ``return` `Collections.min(Powers);``}`` ` `// Driver's Code``public` `static` `void` `main(String[] args)``{``    ``int` `N = ``24``, P = ``4``;`` ` `    ``// Function to find power of``    ``// P in N!``    ``System.out.print(findPowers(N, P));``}``}` `// This code is contributed by Rajput-Ji`

## Python3

 `# Python3 program to find the power``# of P in N!``import` `math` `# Map to store all``# the prime factors of P``Map` `=` `{}` `# Function to find the prime``# factors of N im Map``def` `findPrimeFactors(N):` `    ``# Clear map``    ``Map``.clear()` `    ``# Check for factors of 2``    ``while` `(N ``%` `2` `=``=` `0``):``        ``if` `2` `in` `Map``:``            ``Map``[``2``] ``+``=` `1``        ``else``:``            ``Map``[``2``] ``=` `1``        ``N ``=` `N ``/``/` `2` `    ``# Find all the prime factors``    ``for` `i ``in` `range``(``3``, ``int``(math.sqrt(N)) ``+` `1``, ``2``):``      ` `        ``# If i is a factors``        ``# then increase the``        ``# frequency of i``        ``while` `(N ``%` `i ``=``=` `0``):``            ``if` `i ``in` `Map``:``                ``Map``[i] ``+``=` `1``            ``else``:``                ``Map``[i] ``=` `1``                ` `            ``N ``=` `N ``/``/` `i` `    ``if` `(N > ``2``):``        ``if` `N ``in` `Map``:``            ``Map``[N] ``+``=` `1``        ``else``:``            ``Map``[N] ``=` `1` `# Function to find the power``# of prime number P in N!``def` `PowInFactN(N, P):` `    ``ans ``=` `0``    ``temp ``=` `P` `    ``# Loop until temp <= N``    ``while` `(temp <``=` `N):` `        ``# Add the number of``        ``# numbers divisible``        ``# by N``        ``ans ``=` `ans ``+` `(N ``/``/` `temp)` `        ``# Each time multiply``        ``# temp by P``        ``temp ``=` `temp ``*` `P` `    ``# Returns ans``    ``return` `ans` `# Function that find the``# powers of any P in N!``def` `findPowers(N, P):` `    ``# Find all prime factors``    ``# of number P``    ``findPrimeFactors(P)` `    ``# To store the powers of``    ``# all prime factors``    ``Powers ``=` `[]` `    ``# Traverse the map``    ``for` `it1, it2 ``in` `Map``.items():` `        ``# Prime factor and``        ``# corres. powers``        ``primeFac ``=` `it1``        ``facPow ``=` `it2` `        ``# Find power of prime``        ``# factor primeFac``        ``p ``=` `PowInFactN(N, primeFac)` `        ``# Divide frequency by``        ``# facPow``        ``p ``=` `p ``/``/` `facPow` `        ``# Store the power of``        ``# primeFac^facPow``        ``Powers.append(p)` `    ``# Return the minimum``    ``# element in Power array``    ``return` `min``(Powers)` `N, P ``=` `24``, ``4` `# Driver code``if` `__name__ ``=``=` `"__main__"``:``  ` `  ``# Function to find``  ``# power of P in N!``  ``print``(findPowers(N, P))` `# This code is contributed by divyeshrabadiya07`

## C#

 `// C# program to find the power``// of P in N!``using` `System;``using` `System.Linq;``using` `System.Collections.Generic;` `class` `GFG{` `// Map to store all the prime``// factors of P``static` `Dictionary<``int``,``int``> Map = ``new` `Dictionary<``int``,``int``>();` `// Function to find the prime``// factors of N im Map``static` `void` `findPrimeFactors(``int` `N)``{``    ``int` `i;` `    ``// Clear map``    ``Map.Clear();` `    ``// Check for factors of 2``    ``while` `(N % 2 == 0) {``        ``if``(Map.ContainsKey(2))``            ``Map = Map + 1;``        ``else``            ``Map.Add(2, 1);``        ``N /= 2;``    ``}` `    ``// Find all the prime factors``    ``for` `(i = 3; i <= Math.Sqrt(N); i += 2) {` `        ``// If i is a factors``        ``// then increase the``        ``// frequency of i``        ``while` `(N % i == 0) {``            ``if``(Map.ContainsKey(i))``                ``Map[i] = Map[i] + 1;``            ``else``                ``Map.Add(i, 1);``            ``N /= i;``        ``}``    ``}` `    ``if` `(N > 2) {``        ``if``(Map.ContainsKey(N))``            ``Map[N] =Map[N] + 1;``        ``else``            ``Map.Add(N, 1);``    ``}``}` `// Function to find the power``// of prime number P in N!``static` `int` `PowInFactN(``int` `N, ``int` `P)``{``    ``int` `ans = 0;``    ``int` `temp = P;` `    ``// Loop until temp <= N``    ``while` `(temp <= N) {` `        ``// Add the number of``        ``// numbers divisible``        ``// by N``        ``ans += N / temp;` `        ``// Each time multiply``        ``// temp by P``        ``temp = temp * P;``    ``}` `    ``// Returns ans``    ``return` `ans;``}` `// Function that find the``// powers of any P in N!``static` `int` `findPowers(``int` `N, ``int` `P)``{` `    ``// Find all prime factors``    ``// of number P``    ``findPrimeFactors(P);` `    ``// To store the powers of``    ``// all prime factors``    ``List<``int``> Powers = ``new` `List<``int``>();` `    ``// Traverse the map``    ``foreach` `(KeyValuePair<``int``, ``int``> it ``in` `Map) {` `        ``// Prime factor and``        ``// corres. powers``        ``int` `primeFac = it.Key;``        ``int` `facPow = it.Value;` `        ``// Find power of prime``        ``// factor primeFac``        ``int` `p = PowInFactN(N,``                        ``primeFac);` `        ``// Divide frequency by``        ``// facPow``        ``p /= facPow;` `        ``// Store the power of``        ``// primeFac^facPow``        ``Powers.Add(p);``    ``}` `    ``// Return the minimum``    ``// element in Power array``    ``return` `Powers.Min();``}` `// Driver's Code``public` `static` `void` `Main(String[] args)``{``    ``int` `N = 24, P = 4;` `    ``// Function to find power of``    ``// P in N!``    ``Console.Write(findPowers(N, P));``}``}` `// This code is contributed by sapnasingh4991`
Output:
`11`

Time Complexity: O(sqrt(P)*(logP N))

My Personal Notes arrow_drop_up