Count number of subsets whose median is also present in the same subset | Java implementation of the approach ; Function to return the factorial of a number ; Function to return the value of nCr ; Function to return a raised to the power n with complexity O ( log ( n ) ) ; Function to return the number of sub - sets whose median is also present in the set ; Number of odd length sub - sets ; Sort the array ; Checking each element for leftmost middle element while they are equal ; Calculate the number of elements in right of rightmost middle element ; Calculate the number of elements in left of leftmost middle element ; Add selected even length subsets to the answer ; Driver code
import java . util . * ; class GFG { static long mod = 1000000007 ; static int fact ( int n ) { int res = 1 ; for ( int i = 2 ; i <= n ; i ++ ) res = res * i ; return res ; } static int nCr ( int n , int r ) { return fact ( n ) / ( fact ( r ) * fact ( n - r ) ) ; } static long powmod ( long a , long n ) { if ( n == 0 ) return 1 ; long pt = powmod ( a , n / 2 ) ; pt = ( pt * pt ) % mod ; if ( n % 2 == 1 ) return ( pt * a ) % mod ; else return pt ; } static long CountSubset ( int [ ] arr , int n ) { long ans = powmod ( 2 , n - 1 ) ; Arrays . sort ( arr ) ; for ( int i = 0 ; i < n ; ++ i ) { int j = i + 1 ; while ( j < n && arr [ j ] == arr [ i ] ) { int r = n - 1 - j ; int l = i ; ans = ( ans + nCr ( l + r , l ) ) % mod ; j ++ ; } } return ans ; } public static void main ( String [ ] args ) { int arr [ ] = { 2 , 3 , 2 } ; int n = arr . length ; System . out . println ( CountSubset ( arr , n ) ) ; } }