binarysearchtree

public class binarytree<Value> {
         private Node root = null;
         private  class Node{
               private Value val;
               private int key;
               private Node left,right;
               private int N;   //the number of the all nodes of its child nodes and itself
               //private int num;//the number
               public Node(Value val,int key,int N){
                   this.val = val; this.N = N;this.key = key;
               }
           
       }

        public  void walk(Node x) {   //O(n) time
            if(x!=null){
                walk(x.left);
                System.out.println(x.key);
                walk(x.right);
            }
        }
        
        public Value get(Node x,int key){
            if(x == null){
                return null;
            }
            
            if(x.key>key){
                return get(x.left,key);
            }
            else if(x.key < key){
                return get(x.right,key);
            }
            else{
                return x.val;
            }
        }
         private Node min(Node x){
             if(x.left == null) return x;
             return min(x.left);
         }
         
         private Node deletemin(Node x){
         if(x.left == null){return x.right;}
         x.left = deletemin(x.left);
         x.N = size(x.left) + size(x.right) + 1;
         return x;
         }
         
         
         
         private Node delete(Node x,int key){
             if(key < x.key) x.left = delete(x.left,key);
              else if(key > x.key) x.right = delete(x.right,key);
              else{
                  if(x.left == null) return x.right;
                  if(x.right == null) return x.left;
                  Node t = x;
                  x = min(t.right);
                  x.right = deletemin(t.right);
                  x.left = t.left;
              }
             x.N = size(x.left) +size(x.right)+1;
             return x;
             
         }
         
         
         
         
         private  Node put(Node x,Value val,int key){
               if(x == null) return new Node(val,key,1);
               if(key < x.key) x.left = put(x.left,val,key);
               else if(key > x.key) x.right = put(x.right,val,key);
               else x.key = key;
               x.N = size(x.left) + size(x.right) + 1;
               return x;
           }
           private  int size(Node x){
               if(x == null){return 0;}
               else return x.N;
           }
           
          
           
           private Node select(Node x,int k){
               if(x == null) return null;
               int t = size(x.left);
               if (t>k) return select(x.left,k);
               else if(t<k) return select (x.right,k-t-1);
               else return x;
           }
           
         
           
    }