public class Solution {

public boolean ok(String s, int start, int end){

String tmp = s.substring(start,end);

if(tmp.length()>3){

return false;

}else if(tmp.length()==0){

return false;

}else if(tmp.length()==1){

return true;

}else if(tmp.length()==2){

return tmp.compareTo("10")>=0 && tmp.compareTo("99")<=0 ;

}else{

return tmp.compareTo("100")>=0 && tmp.compareTo("255")<=0;

}

}

public ArrayList<String> restoreIpAddresses(String s) {

// Start typing your Java solution below

// DO NOT write main() function

int i1=0;

int i2=0;

int i3=0;

ArrayList<String> al = new ArrayList<String>();

if(s.length()>3*4) return al;

for(i1=0;i1<s.length();i1++){

if(i1>3) continue;

if(!ok(s,0,i1)) continue;

for(i2=i1+1;i2<s.length();i2++){

if(i2-i1>3) continue;

if(!ok(s,i1,i2)) continue;

for(i3=i2+1;i3<s.length();i3++){

if(i3-i2>3) continue;

if(s.length()-i3>3) continue;

if(!ok(s,i2,i3)) continue;

if(!ok(s,i3,s.length())) continue;

StringBuilder sb = new StringBuilder("");

sb.append(s.substring(0,i1));

sb.append(".");

sb.append(s.substring(i1,i2));

sb.append(".");

sb.append(s.substring(i2,i3));

sb.append(".");

sb.append(s.substring(i3,s.length()));

al.add(sb.toString());

}

}

}

return al;

}

}