- Trending Categories
- Data Structure
- Networking
- RDBMS
- Operating System
- Java
- MS Excel
- iOS
- HTML
- CSS
- Android
- Python
- C Programming
- C++
- C#
- MongoDB
- MySQL
- Javascript
- PHP
- Physics
- Chemistry
- Biology
- Mathematics
- English
- Economics
- Psychology
- Social Studies
- Fashion Studies
- Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Find sum of digits in factorial of a number in C++
Suppose, we have a number n, our task is to find the sum of digits in then!. Consider n = 5, then n! = 120. So the result will be 3.
To solve this problem, we will create a vector to store factorial digits and initialize it with 1. Then multiply 1 to n one by one to the vector. Now sum all the elements in the vector and return the sum
Example
#include<iostream> #include<vector> using namespace std; void vectorMultiply(vector<int> &v, int x) { int carry = 0, res; int size = v.size(); for (int i = 0 ; i < size ; i++) { int res = carry + v[i] * x; v[i] = res % 10; carry = res / 10; } while (carry != 0) { v.push_back(carry % 10); carry /= 10; } } int digitSumOfFact(int n) { vector<int> v; v.push_back(1); for (int i=1; i<=n; i++) vectorMultiply(v, i); int sum = 0; int size = v.size(); for (int i = 0 ; i < size ; i++) sum += v[i]; return sum; } int main() { int n = 40; cout << "Number of digits in " << n << "! is: " << digitSumOfFact(n); }
Output
Number of digits in 40! is: 189
Advertisements