【数据结构与算法】十五 二叉树遍历 DFS 深度优先 递归算法

结合上一篇的二叉树文章.
遍历即将树的所有结点访问且仅访问一次.
Depth-First-Search 深度优先
基于深度优先算法有三种

前序遍历：根节点->左子树->右子树

    private void preorder(Node node){        if(null == node)            return ;         System.out.print(node.value);        preorder(node.left);        preorder(node.right);    }

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中序遍历：左子树->根节点->右子树

    private void midorder(Node node){        if(null == node)            return ;         midorder(node.left);        System.out.print(node.value);        midorder(node.right);    }

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后序遍历：左子树->右子树->根节点

    private void postorder(Node node){        if(null == node)            return ;         postorder(node.left);        postorder(node.right);        System.out.print(node.value);    }

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完整code

package com.cn.mark.algorithm.binarytree;public class BST <T extends Comparable<? super T>>{    private static class Node<T> {        private T value ;         private Integer position ;         private Integer height ;        private Node<T> left;        private Node<T> right;        public Node(T value , Integer position, Node<T> left, Node<T> right) {            this.value =  value;            this.position = position ;             this.height = 0;            this.left = left;            this.right = right;        }    }    private int height(Node<T> t) {        return t == null ? -1 : t.height;    }    private Node<T> root ;     public void add(T value , Integer position){        root = add( value , position, root );    }    private Node<T> add(T value , Integer position, Node<T> node){        if(node == null){            return new Node<T>(value,position , null ,null);        }        int comparaResult = value.compareTo(node.value);        if(comparaResult > 0)            node.right = add(value , position , node.right);        else if (comparaResult < 0)            node.left = add(value , position , node.left);        else             System.out.println("as same a value");        node.height = Math.max(height(node.left), height(node.right)) + 1;        return node;    }    public Integer search(Node<T> node , T value){        if(node == null)            return -1 ;         int comparaResult = value.compareTo(node.value);        if(comparaResult == 0)            return node.position;        else if(comparaResult > 0)            return search(node.right, value);        else if(comparaResult < 0)            return search(node.left, value);        else            return -1;    }    private void preorder(Node<T> node){        if(null == node)            return ;         System.out.print(node.value);        preorder(node.left);        preorder(node.right);    }    private void midorder(Node<T> node){        if(null == node)            return ;         midorder(node.left);        System.out.print(node.value);        midorder(node.right);    }    private void postorder(Node<T> node){        if(null == node)            return ;         postorder(node.left);        postorder(node.right);        System.out.print(node.value);    }    public static void main(String[] args){        BST<Integer> bst = new BST<Integer>();          int[] array = {0,1,5,6,7,2,3,4,8,9};        for(int i=0;i<array.length;i++)            bst.add(array[i],i);//         System.out.println(bst.height(bst.root));        System.out.println(bst.search(bst.root, 8));        System.out.println(bst.search(bst.root, 0));        System.out.println(bst.search(bst.root, 22));        bst.preorder(bst.root);        System.out.println();        bst.midorder(bst.root);        System.out.println();        bst.postorder(bst.root);    }}