Given a string containing only digits, restore it by returning all possible valid IP address combinations.
For example:
Given “25525511135”,
return [“255.255.11.135”, “255.255.111.35”]{hint:recursion,backtrack}

Here is the Solution ……
it was taken me about 5 hours to solve see !!!

//cc Arun Kumar Gupta

import java.util.*;
public class AllIpAddress
{
public static void main (String [] args)
{
Scanner sc = new Scanner(System.in);
String input = sc.next();
int[] intArray = new int[input.length()];
int length = input.length();

for (int i = 0; i < input.length(); i++) {
intArray[i] = Character.digit(input.charAt(i), 10);
//System.out.println(intArray[i]);
}
int i = 0 , j = 1 , k = 2;
AllIpAddress ip = new AllIpAddress();
ip.Ipaddress(intArray , i , j , k , length-1);

}
void Ipaddress(int [] intArray , int i , int j , int k , int length)
{
try{
int where = 0 ,change = 0;
int p1 =createIP( intArray , -1 , i);
int p2 =createIP( intArray , i ,  j );
int p3 =createIP( intArray ,  j , k );
int p4 =createIP( intArray ,  k ,  length );
//System.out.println(“**********Garbage”+p1+”.”+p2+”.”+p3+”.”+p4);
//System.out.println(“i = “+i+”j = “+j+”k = “+k);
if((p1<=255)&&(p2<=255)&&(p3<=255)&&(p4<=255)&&(p4>0))
{
System.out.println(p1+”.”+p2+”.”+p3+”.”+p4);
}
if(p4 >255)
{
//if(k != j)
//++k;
where =4;
//System.out.println(“Problem at P4”);
}
else if(p3>255)
{
//if(j != i)
//++j;
//–k;
where = 3;
//System.out.println(“Problem at P3”);
}
else if(p2>255)
{
//++i;
where = 2;
//System.out.println(“Problem at P2”);
}
else if(p1>255)
{

//System.out.println(“Problem at P1”);
System.exit(0);
}

if((k == length) && (j+1 == k))
{
//System.out.println(“if((k == length) && (j+1 == k))”);
//System.out.println(i+”_”+j+”_”+k);
++i;
j = i+1;
k = j+1;
change = 1;
//System.out.println(i+”_”+j+”_”+k);

}
if((k == length) &&(change == 0) )
{
//System.out.println(“if((k == length) &&(change == 0) )”);
++j;
k = j+1;
change = 0;
}
else if(change == 0)
{
if( (k) < length )
++k;
}
/*if(where ==4)
{
++k;
}
if(where ==3)
{
++j;
–k;
}
if(where ==2)
{
++i;
–j;
}
/*if(k==length)
{
–k;
–j;
}*/
Ipaddress(intArray , i , j , k , length);
}
catch(ArrayIndexOutOfBoundsException e){
//System.out.println(“Exception thrown  :” + e);
}
}
static int createIP(int [] intArray , int start , int end)
{
//System.out.println(“I am at createIP()start = “+start+”\tend = “+end);
int val = 1 , fina = 0;
for(int e =end ; e>start ; –e)
{
fina = intArray[e]*val + fina;
val = val*10;
}
return fina;
}
}

• Octal constants are written with a leading zero – 015.
• Hexadecimal constants are written with a leading 0x – 0x1ae.
• Long constants are written with a trailing L – 890L.

Character constants are usually just the character enclosed in single quotes; ‘a’, ‘b’, ‘c’. Some characters can’t be represented in this way, so we use a 2 character sequence as follows.

'\n' newline
'\t' tab
'\\' backslash
'\'' single quote
'\0' null ( Usedautomatically to terminate character string )

Defining Constants

int const a = 1;
const int a =2;

• You can declare the const before or after the type. Choose one an stick to it.
• It is usual to initialise a const with a value as it cannot get a value any other way.

#define TRUE  1
#define FALSE  0
#define NAME_SIZE 20

void strcpy(char *buffer, char const *string)

The enum Data type

enum colors {RED, YELLOW, GREEN, BLUE};

enum colors {RED=1, YELLOW, GREEN=6, BLUE };

#include 

int main() {
  enum {RED=5, YELLOW, GREEN=4, BLUE};

  printf("RED = %d\n", RED);
  printf("YELLOW = %d\n", YELLOW);
  printf("GREEN = %d\n", GREEN);
  printf("BLUE = %d\n", BLUE);
  return 0;
}

This will produce following results

  RED = 5
  YELLOW = 6
  GREEN = 4
  BLUE = 5

Copied From Tutorial C

as we know by default the pointers are near for example int *p is a near pointer… size of near pointer is 2 bytes in case of 16 bit compiler…….. n we already know very well size varies compiler to compiler…… They only store the offset of the address the pointer is referencing. . An address consisting of only an offset has a range of 0 – 64K bytes…. i think there is no need to discuss near pointers anymore…. so come to the main point….. that is far and huge pointers……