Display 1,2,3,4,5,6,8,10,11 as 1-6,8,10-11?

Question

> I have this sequence **1,2,3,4,5,6,8,10,11** > > Expected output is **1-6,8,10-11** This problem is about formatting the sequence in easy readable form I tried with c# and used many if & else. Interviewer said, there is some simple algorithm to do this. I have no idea how to achive this very simple. > Also for 1,2,3 i shown 1-3. They said its wrong!. Is there any design pattern(interpreter) involved in this logic?

Answer 1

You need to use a state machine in order to process the condensed sequence string...

declare a variable called state with the following values:

0 = beginning of the sequences

1 = numbers are out of sequence

2 = looking for next # in the sequence

3 = end of the sequence..

Here's the code:

class Sequence

{

public static void main(String args[])

{

String inbuff = "1,2,3,4,5,6,8,10,11";

//String ibuff = "1,2,3,4,7,8,10,12,13,14,15,16,17,20,21,24,27,28,29,31,32,33,36,37,41";

String outbuff = " ";

String [] tokens = inbuff.split(",");

int lastX = 0;

int state=0; //state = 0 : beginning of the sequence

// state = 1: comma separates numbers out of sequence

// state = 2: waiting for next # in the sequence

// state = 3: ending of the sequence

for (int iLoop=0; iLoop<tokens.length; iLoop++)

{

int x = Integer.parseInt(tokens[iLoop]);

switch (state)

{

case 0:

{

outbuff = outbuff + x ;

state=2;

break;

}

case 1:

{

if ((x-lastX)==1)

{

outbuff = outbuff + "-" + x;

}

else

{

outbuff = outbuff + "," + x;

}

state=2;

break;

}

case 2:

{

if ((x - lastX)==1)

{

}

else

{

outbuff = outbuff + "-" + lastX + "," + x;

state = 1;

}

break;

}

case 3:

{

if ((x-lastX)==1)

{

outbuff = outbuff + "-";

}

else

{

outbuff = outbuff + ",";

}

outbuff = outbuff + x;

break;

}

}//switch

lastX = x;

if (iLoop==tokens.length-2)

{

state=3;

}

} //for loop

System.out.println(outbuff);

} //main

}