IP Matching

ipmatching.java

// java.util.* and java.util.streams.* have been imported for this problem.
// You don't need any other imports.

public static ArrayList<String> generateIPAddrs(String s) {

    Stack<IpLevelNode> st = new Stack<>();
    ArrayList<String> answer = new ArrayList<>();

        Character c = s.charAt(0);
        Integer numValue = Character.getNumericValue(c);
        
      
        st.push( new IpLevelNode(String.valueOf(numValue), 1, s.substring(1)));
        
       // st.push( new IpLevelNode(String.valueOf(numValue)+".", 1, s.substring(1)));
        System.out.println("first:" + st.peek().predecessor + "," +  st.peek().successor + " Level " + st.peek().level);
        while(!st.empty()) {
            
            IpLevelNode node1 = st.pop();
            Character c1 = node1.successor.charAt(0);
            String newp;
            Integer num=0;
            if(node1.predecessor.charAt(node1.predecessor.length()-1) =='.') {
                newp = String.valueOf(c1);
                num = Integer.valueOf(newp);
            }
            else {
                newp = node1.predecessor + String.valueOf(c1); // newp=1921
                int lastIndex = newp.lastIndexOf(".");
                if(lastIndex > -1) {
                    String newpsub = newp.substring(lastIndex+1);
                    num = Integer.valueOf(newpsub);
                    
                }
                else {
                    num = Integer.valueOf(newp);
                }
            }
            
            
           
            if(node1.successor.length() > 1 && node1.level < 5) {
                if(num > 255) {
                    
                  addpartitions(st, node1, c1);
                    newp = String.valueOf(c1);
                   if(node1.predecessor.charAt(node1.predecessor.length()-1)=='.')
                        st.push(new IpLevelNode(node1.predecessor  + newp, node1.level+1, node1.successor.substring(1)));
                    else
                        st.push(new IpLevelNode(node1.predecessor + "." + newp, node1.level+1, node1.successor.substring(1)));
                        
                     System.out.println("add2:" + st.peek().predecessor + "," +  st.peek().successor + " Level " + st.peek().level);
                    
                }
                else {
                     addpartitions(st, node1, c1);
                     if(node1.predecessor.charAt(node1.predecessor.length()-1)=='.') {
                          st.push(new IpLevelNode(node1.predecessor + newp, node1.level, node1.successor.substring(1)));
                     }
                     else if (getLastPart(newp).length() <4) {
                          st.push(new IpLevelNode(newp, node1.level, node1.successor.substring(1)));
                     }
                    
                   
                    System.out.println("add3:" + st.peek().predecessor + "," +  st.peek().successor + " Level " + st.peek().level);
                }
            }
            else {
                 if(node1.level+1 == 4) {
                     if(num > 255) {
                         newp = String.valueOf(c1);
                          System.out.println("Answer1: " + node1.predecessor + "." + newp);
                            answer.add(node1.predecessor + "." + newp);
                            addpartitions(st, node1, c1);
                            
                     }
                     else {
                          System.out.println("Answer3: "+ newp);
                           newp = String.valueOf(c1);
                            answer.add(node1.predecessor +"." + newp);
                     }
                        
                 }
                 else if (node1.level==4 && node1.successor.length()==1) {
                     int lastIndex = node1.predecessor.lastIndexOf(".");
                     String ss = node1.predecessor.substring(lastIndex+1) + node1.successor;
                     if (Integer.valueOf(ss) < 256) {
                        System.out.println("Answer2: " + node1.predecessor + node1.successor);
                        answer.add(node1.predecessor + node1.successor);
                     }
                 }
            }
          
            
        }
        
        return new ArrayList(new HashSet<String>(answer));
    
    
}

private static void addpartitions(Stack<IpLevelNode> st, IpLevelNode node1, Character c1) {
    
                    String newp = String.valueOf(c1);
                    int dotIndex = node1.predecessor.lastIndexOf(".");
                    String partitionNumber;
                    boolean level  = false;
                    if(dotIndex > -1) {
                        partitionNumber = node1.predecessor.substring(dotIndex+1);
                        level = true;
                    }
                    else {
                        partitionNumber= node1.predecessor;
                        level = false;
                    }
                    
                    System.out.println("partition: " + partitionNumber);
                    for(int i=0;i<partitionNumber.length(); ++i) {
                        String newNumber = new StringBuilder(partitionNumber).insert(i+1, '.').toString();
                        if(level) {
                            System.out.println("addp1: " + node1.predecessor + ", " + removeLastPart(node1.predecessor) );
                            st.push(new IpLevelNode(removeLastPart(node1.predecessor) + newNumber, node1.level+1, node1.successor));
                        }
                        else {
                         st.push(new IpLevelNode(newNumber, node1.level+1, node1.successor));
                        }
                          System.out.println("addp2:" + st.peek().predecessor + "," +  st.peek().successor + " Level " + st.peek().level);
                    }
                   
    
    
}


private static String getLastPart(String str) {
      int lastIndex = str.lastIndexOf(".");
      if (lastIndex > -1) {
          return str.substring(lastIndex + 1);
      }
      
      return str;
                 
}

private static String removeLastPart(String str) {
    
    int lastIndex = str.lastIndexOf(".");
    
    if(lastIndex == -1) {
        return str;
    }
    StringBuilder sb = new StringBuilder();
    for(int i=0;i <lastIndex; ++i) {
        sb.append(str.charAt(i));
    }
    return sb.toString()+".";
}


static class IpLevelNode {
    
    String predecessor;
    int level;
    String successor;
    
    public IpLevelNode(String p, int l, String s) {
        this.predecessor = p;
        this.level = l;
        this.successor = s;
    }
    
}