Count number of subsets whose median is also present in the same subset | Java implementation of the above approach ; Function to store pascal triangle in 2 - d array ; 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 . Arrays ; class GFG { static long mod = 1000000007 ; static long [ ] [ ] arr = new long [ 1001 ] [ 1001 ] ; static void Preprocess ( ) { arr [ 0 ] [ 0 ] = 1 ; for ( int i = 1 ; i <= 1000 ; ++ i ) { arr [ i ] [ 0 ] = 1 ; for ( int j = 1 ; j < i ; ++ j ) { arr [ i ] [ j ] = ( arr [ i - 1 ] [ j - 1 ] + arr [ i - 1 ] [ j ] ) % mod ; } arr [ i ] [ i ] = 1 ; } } 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 [ ] val , int n ) { long ans = powmod ( 2 , n - 1 ) ; Arrays . sort ( val ) ; for ( int i = 0 ; i < n ; ++ i ) { int j = i + 1 ; while ( j < n && val [ j ] == val [ i ] ) { int r = n - 1 - j ; int l = i ; ans = ( ans + arr [ l + r ] [ l ] ) % mod ; j ++ ; } } return ans ; } public static void main ( String [ ] args ) { Preprocess ( ) ; int val [ ] = { 2 , 3 , 2 } ; int n = val . length ; System . out . println ( CountSubset ( val , n ) ) ; } }