java 二叉树三种遍历（递归非递归）

import java.util.*;/** * Created by yyt on 2017/5/23. */public class wap2016 {    public static void main(String[] args){        int a[] = {1,2,3,0,0,6,7,0,0,0,0,12,13,0,15};        wap2016.generateTreefromArray b = new wap2016().new generateTreefromArray(a);        wap2016.TreeNode root =  b.generateTreebycengci();//        b.BFS();//        b.nonRecPreOrder( root );         b.nonRecPostOrder(root);    }    class  TreeNode{        private int key=0;        private int data=0;        private boolean isVisted=false;         private TreeNode leftChild=null;         private TreeNode rightChild=null;         public TreeNode getLeftChild() {             return leftChild;         }         public void setLeftChild(TreeNode leftChild) {             this.leftChild = leftChild;         }         public TreeNode getRightChild() {             return rightChild;         }         public void setRightChild(TreeNode rightChild) {             this.rightChild = rightChild;         }        /**         * @param key  层序编码         * @param data 数据域         */          TreeNode(int key,int data){            this.key=key;            this.data=data;            this.leftChild=null;            this.rightChild=null;        }    }    public class generateTreefromArray{        private int[] a;        private TreeNode root = null;        private int num = 0;        private generateTreefromArray(int[] a ){            this.a = a;        }        TreeNode generateTreebycengci(){            this.root = new TreeNode(1,a[0]);            int length = a.length;            // 相当于又添加了一个 outer 对象？//            wap2016.TreeNode root = new wap2016().new TreeNode(1,b[0])            this.insertNode(root,2,length);            this.insertNode(root,3,length);            return root;        }        private  void insertNode(TreeNode root,int start,int length){            if (start <= length){                if(a[start-1]!=0){                    num+=1;                    TreeNode node = new TreeNode( start, a[start-1] );                    if (start %2 ==0){                        root.setLeftChild(node);                    }                    else{                        root.setRightChild(node);                    }                    insertNode( node,start*2,length );                    insertNode( node,start*2+1,length );                }            }        }        // 层次遍历        public void BFS(){            Queue<TreeNode> temp =new LinkedList<TreeNode>();            temp.add( root );            TreeNode node;            while(temp.size()!=0) {                node = temp.poll();                System.out.print( node.key );                System.out.print( '\t' );                System.out.println( node.data );                if (node.getLeftChild() != null) {                    temp.add( node.getLeftChild() );                }                if (node.getRightChild() != null) {                    temp.add( node.getRightChild() );                }            }        }        // 递归 中序遍历        public void pre_recursive(TreeNode root){            if(root.getLeftChild() != null){                TreeNode node = root.getLeftChild();                pre_recursive(node);            }            System.out.println(root.data);            if(root.getRightChild() != null){                TreeNode node = root.getRightChild();                pre_recursive(node);            }        }        //递归 先序遍历        public void mid_recursive(TreeNode root){            System.out.println(root.data);            if(root.getLeftChild() != null) {                TreeNode node = root.getLeftChild();                pre_recursive( node );            }            if(root.getRightChild() != null){                TreeNode node = root.getRightChild();                pre_recursive(node);            }        }        // 非递归 先序遍历        public void nonRecPreOrder(TreeNode root){            Stack<TreeNode> stack =new Stack<TreeNode>();            TreeNode node = root;            while(node != null || stack.size()>0){                while(node != null){                    stack.add( node );                    node = node.getLeftChild();                }                if(stack.size()>0){                    node = stack.pop();                    System.out.println(node.data);                    node = node.getRightChild();                }            }        }        //非递归 中序遍历        public void nonRecInOrder(TreeNode root){            Stack<TreeNode> stack =new Stack<TreeNode>();            TreeNode node = root;            while(node != null || stack.size()>0){                while(node != null){                    stack.add( node );                    System.out.println(node.data);                    node = node.getLeftChild();                }                if(stack.size()>0){                    node = stack.pop();                    node = node.getRightChild();                }            }        }        // 非递归 后序遍历        public void nonRecPostOrder(TreeNode root){            Stack<TreeNode> stack =new Stack<TreeNode>();            Stack<TreeNode> output = new Stack<TreeNode>();            TreeNode node = root;            TreeNode temp  = null;            while(node != null || stack.size() > 0){                if(node != null){                    stack.push(node);                    output.push(node);                    node = node.getRightChild();                }                else{                    node = stack.pop();                    node = node.getLeftChild();                }                // 这里使用peek            }            while(output.size() > 0){                System.out.println( output.pop().data );            }        }        public void destroy(TreeNode subTree){            //删除根为subTree的子树            if(subTree!=null){                //删除左子树                destroy(subTree.leftChild);                //删除右子树                destroy(subTree.rightChild);                //删除根结点                subTree=null;            }        }        private int height(TreeNode subTree){            if(subTree==null)                return 0;//递归结束：空树高度为0            else{                int i=height(subTree.leftChild);                int j=height(subTree.rightChild);                return (i<j)?(j+1):(i+1);            }        }    }}