Question

sum of digits in the factorial of a number program in C or C++​

Answer 1

Explanation:

// C++ program to find sum of digits in factorial

// of a number

#include <bits/stdc++.h>

using namespace std;

// Function to multiply x with large number

// stored in vector v. Result is stored in v.

void multiply(vector<int> &v, int x)

{

int carry = 0, res;

int size = v.size();

for (int i = 0 ; i < size ; i++)

{

// Calculate res + prev carry

int res = carry + v[i] * x;

// updation at ith position

v[i] = res % 10;

carry = res / 10;

}

while (carry != 0)

{

v.push_back(carry % 10);

carry /= 10;

}

}

// Returns sum of digits in n!

int findSumOfDigits(int n)

{

vector<int> v; // create a vector of type int

v.push_back(1); // adds 1 to the end

// One by one multiply i to current vector

// and update the vector.

for (int i=1; i<=n; i++)

multiply(v, i);

// Find sum of digits in vector v[]

int sum = 0;

int size = v.size();

for (int i = 0 ; i < size ; i++)

sum += v[i];

return sum;

}

// Driver code

int main()

{

int n = 1000;

cout << findSumOfDigits(n);

return 0;

}