Harmonic Progression | Java program to check if a given array can form harmonic progression ; Find reciprocal of arr [ ] ; After finding reciprocal , check if the reciprocal is in A . P . To check for A . P . , first Sort the reciprocal array , then check difference between consecutive elements ; Driver code ; series to check whether it is in H . P ; Checking a series is in H . P or not
import java . util . * ; class GFG { static boolean checkIsHP ( double [ ] arr ) { int n = arr . length ; if ( n == 1 ) return true ; ArrayList < Integer > rec = new ArrayList < Integer > ( ) ; for ( int i = 0 ; i < n ; i ++ ) rec . add ( ( int ) ( 1 / arr [ i ] ) ) ; Collections . sort ( rec ) ; int d = ( int ) rec . get ( 1 ) - ( int ) rec . get ( 0 ) ; for ( int i = 2 ; i < n ; i ++ ) if ( rec . get ( i ) - rec . get ( i - 1 ) != d ) return false ; return true ; } public static void main ( String [ ] args ) { double arr [ ] = { 1 / 5 , 1 / 10 , 1 / 15 , 1 / 20 , 1 / 25 } ; if ( checkIsHP ( arr ) ) System . out . println ( " Yes " ) ; else System . out . println ( " No " ) ; } }