Find sum of digits in factorial of a number | Java program to find sum of digits in factorial of a number ; Function to multiply x with large number stored in vector v . Result is stored in v . ; Calculate res + prev carry ; updation at ith position ; Returns sum of digits in n ! ; One by one multiply i to current vector and update the vector . ; Find sum of digits in vector v [ ] ; Driver code
import java . util . * ; class GFG { static ArrayList < Integer > v = new ArrayList < Integer > ( ) ; static void multiply ( int x ) { int carry = 0 ; int size = v . size ( ) ; for ( int i = 0 ; i < size ; i ++ ) { int res = carry + v . get ( i ) * x ; v . set ( i , res % 10 ) ; carry = res / 10 ; } while ( carry != 0 ) { v . add ( carry % 10 ) ; carry /= 10 ; } } static int findSumOfDigits ( int n ) { for ( int i = 1 ; i <= n ; i ++ ) multiply ( i ) ; int sum = 0 ; int size = v . size ( ) ; for ( int i = 0 ; i < size ; i ++ ) sum += v . get ( i ) ; return sum ; } public static void main ( String [ ] args ) { int n = 1000 ; System . out . println ( findSumOfDigits ( n ) ) ; } }