Harmonic Progression | JavaScript 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 ; series to check whether it is in H . P ; Checking a series is in H . P or not
function checkIsHP ( arr ) { let n = arr . length ; if ( n == 1 ) { return true ; } let rec = [ ] ; for ( let i = 0 ; i < n ; i ++ ) { rec . push ( ( 1 / arr [ i ] ) ) ; } rec . sort ( ( a , b ) => a - b ) ; let d = ( rec [ 1 ] ) - ( rec [ 0 ] ) ; for ( let i = 2 ; i < n ; i ++ ) { if ( rec [ i ] - rec [ i - 1 ] != d ) { return false ; } } return true ; } let arr = [ 1 / 5 , 1 / 10 , 1 / 15 , 1 / 20 , 1 / 25 ] ; if ( checkIsHP ( arr ) ) { document . write ( " " ) ; } else { document . write ( " " ) ; }