public static int getCountOfOnes ( int n ) {

/*

Please implement this method to

return the number of '1's in the binary representation of n

for any integer n, where n > 0

Example: for n=6 the binary representation is '110' and the number of '1's in that

representation is 2

*/

int cnt = 0 ;

String s = Integer . toBinaryString ( n ) ;

System . out . println ( "Binary String = " + s ) ;

for ( int i = 0 ; i < s. length ( ) ; i++ ) {

String j = Character . toString ( s. charAt ( i ) ) ;

if ( Character . isDigit ( s. charAt ( i ) ) ) {

if ( j. equalsIgnoreCase ( "1" ) ) {

cnt++ ;

}

}

}

return cnt ;

}

// Please do not change this interface

interface ListNode {

int getItem ( ) ;

ListNode getNext ( ) ;

void setNext ( ListNode next ) ;

}

public static ListNode reverse ( ListNode node ) {

/*

Please implement this method to

reverse a given linked list.

*/

ListNode prev = null ;

ListNode cur = null ;

ListNode next = null ;

prev = node ;

cur = node. getNext ( ) ;

prev. setNext ( null ) ;

while ( cur. getNext ( ) ! = null ) {

next = cur. getNext ( ) ;

cur. setNext ( prev ) ;

}

return cur ;