Binary Representation of n-1 number

Binary Representation of n-1 number

  October 01, 2017    

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Idea is to make all 0 to 1 until we find 1 , when 1 is encountered then change it to 0 and break loop .

Print string.

Code:

public static void main (String[] args)
{
Scanner ab=new Scanner(System.in);
int t=ab.nextInt();
while(t-->0)
{
    StringBuffer str=new StringBuffer(ab.next());
    int len=str.length();
    int i=len-1;
    while(i>=0)
    {
        if(str.charAt(i)=='1')
        {
            str.setCharAt(i,'0');
            break;
        }
        str.setCharAt(i,'1');
        --i;
    }
//delete leading 0
    i=0;
    while(i<len-1)
    {
        if(str.charAt(i)=='1')
        {len=i;
            break;
        }
        ++i;
    }
    System.out.println(str.substring(len));
}
}