ctci 2.4 - cut the linked list around given value of x - create a list of values before x , x, values after x

I almost got this question:
compare every element to x, and sort them accordingly, similar to quicksort kinda.
but i failed to understand 2 things:

numbers itself DON'T GO ANYWHERE, they just stay in memory, IT IS ALL ABOUT TWISTING THE ARROWS - POINTERS btw nodes!!!!!!

so i failed to implement this idea: unwind/ detach your first node, but save the next element to keep going through the original list!

this is the drawing:

example:
x = 20
value found - 12.
12 < 20 , so detach it from original list and make it point to the new "less than x "  list!


public static node partition(int x, node list){
 
    node smaller = null ;
    node larger = null ;
   
    while(list != null){        
      node saved_list_next = list.next ;
      if(list.data < x){
           list.next = smaller ;
           smaller = list ;    
      }
      else{
         list.next = larger ;
         larger = list ;
      }  
      list = saved_list_next ;    
    }
    if(smaller == null) return larger ;
    node head = smaller ;
    while(smaller.next!= null) smaller = smaller.next ;
    node middle = new node((short) -1) ;
    smaller.next = middle ;
    smaller.next.next = larger ;
    return head ;
   
  }

ctci 1.6 - rotate nxn matrix clockwise

question: for nxn matrix,  rotate all cells by 90degrees clockwise.
HOnestly, i did not understand the question itself, so i looked up the solution; run my example and figured out how it works.

as always, the idea is to hack the pattern - how the indexes change - and simply code it appropriately.
i drawn this picture:

public class ctci_1_6{
 
  public static void main(String []a){
   int image_matrix[][] = {
     {1,1,1,1,1,1},
     {2,2,2,2,2,2},
     {3,3,3,3,3,3},
     {4,4,4,4,4,4},    
     {5,5,5,5,5,5},
     {6,6,6,6,6,6}
   } ;
   print_matrix(image_matrix,6) ;
   rotate(image_matrix,6) ;
   System.out.println("\n\n AFTER :") ;
   print_matrix(image_matrix,6) ;
  }
  public static void print_matrix(int matrix[][], int n){
    for(int i = 0 ; i < n ; i++){
      for(int j = 0 ;j < n ; j++){
            System.out.print(  matrix[i][j] + "\t") ;
      }
            System.out.println() ;
    }
  }
  public static void rotate(int matrix[][], int n){
    for(int layer = 0 ; layer < n/2 ; layer++){
      System.out.println("---------------------------------------------------------------------------------------------") ;
     
    int first = layer ;
    int last = n - 1 - layer ;
    System.out.println("first: " + first + " , last : " + last) ;
    for(int i = first;  i < last ; i++){
      System.out.println("^^^^^") ;
     
         int offset =  i - first ;
         System.out.println(" offset: " + offset) ;
         int top = matrix[first][i] ;
         //left -> top
         matrix[first][i] =  matrix[last - offset][first] ;
         System.out.printf("m[%d][%d] = m[%d][%d]\n", first, i, (last - offset), first) ;
         //bottom -> left
         matrix[last - offset][first] = matrix[last][last - offset] ;
         System.out.printf("m[%d][%d] = m[%d][%d]\n",  (last - offset), first, last, (last -offset)) ;
         //right->bottom
         matrix[last][last - offset] = matrix[i][last] ;
         System.out.printf("m[%d][%d] = m[%d][%d]\n", last, (last - offset), i, last) ;
         //top ->right
         matrix[i][last] = top ;
         System.out.printf("m[%d][%d] = m[%d][%d]\n", i,last, first,i) ;
      }
    System.out.println() ;
    }
 
  }

}

musings about vim

I decided not to learn vim, gvim etc. 

The advantages of it are well known, but i would rather become familiar wih Eclipse/visual studio and other standard frameworks.

at this point, i see no strong preference towards vim as i was thinking 2 years ago. After all, most features(autocompletion, syntax highlight) become the standard of the industry, most engineers will demand them in any tool.

So i reviewed my craving to study vim and get good at it,after all i want to build cool things, apps and eclipse/visual studio are pretty good!

cracking the coding interview interview question - 1.5

ok, i m doing some cracking the coding interview questions just to improve a bit my skills. and it s not that bad!
look up my code; it works , but has testing printing.
the question itself : compress a string, example : aaa = a3, ab = a1b1, abc = a1b1c1 etc.

if the compressed string is longer then return original.

import java.util.* ;

public class ctci{
  public static void main(String args[]){
  String result = compressed("aa")  ;
  }
   
public static String compressed(String original_string){
  if(original_string.length() <=2 ) return original_string ;
  String compressed_string = "" ;
 
  for(int i = 0 ; i < original_string.length() ; i++){
       System.out.println("------------------------------------------------------------------------------------------------------------------------------ i : " + i ) ;
     
     char current_char = original_string.charAt(i) ;
     System.out.println("current char " + current_char) ;
     int streak = 1 ;
     while(i < original_string.length() -1 && current_char == original_string.charAt(i+1) ) {
       System.out.println("streak len growing: " + streak + " and letter is : " + original_string.charAt(i+1)) ;
       i++ ;
       streak++ ;
     }
   
     //compressed_string += (current_char + "") + streak ;
     compressed_string += String.valueOf(current_char) + streak ;
     System.out.println( "streak ended, length of the streak  " + streak + " ; and the new string is " + compressed_string ) ;
  }  
  if(compressed_string.length() >= original_string.length()){System.out.println("original returned! " + original_string) ; return original_string ;}
  else{System.out.println("compressed returned!  " + compressed_string) ; return compressed_string ;}
 
 
}
}