二叉树的遍历

package 算法和数据结构;/*** Filename : TreeBianli.java* Author : [e-mail]* Creation time : 下午6:28:39 - 2017年3月11日* Description :*/import java.util.Stack;import java.util.HashMap;class Node {    char val;    Node left;    Node right;    Node(char val) {        this.val = val;    }    Node(char val, Node left, Node right) {        this.val = val;        this.left = left;        this.right = right;    }    public char getKey() {        return val;    }    public Node getLeft() {        return left;    }    public Node getRight() {        return right;    }}public class BinaryTree {    protected Node root;    public BinaryTree(Node root) {        this.root = root;    }    public Node getRoot() {        return root;    }    /** 构造树 */    public static Node init() {        Node a = new Node('A');        Node b = new Node('B', null, a);        Node c = new Node('C');        Node d = new Node('D', b, c);        Node e = new Node('E');        Node f = new Node('F', e, null);        Node g = new Node('G', null, f);        Node h = new Node('H', d, g);        return h;// root    }    /** 访问节点 */    public static void visit(Node p) {        System.out.print(p.getKey() + " ");    }    /** 递归实现前序遍历 */    protected static void preorder(Node p) {        if (p != null) {            visit(p);            preorder(p.getLeft());            preorder(p.getRight());        }    }    /** 递归实现中序遍历 */    protected static void inorder(Node p) {        if (p != null) {            inorder(p.getLeft());            visit(p);            inorder(p.getRight());        }    }    /** 递归实现后序遍历 */    protected static void postorder(Node p) {        if (p != null) {            postorder(p.getLeft());            postorder(p.getRight());            visit(p);        }    }    /** 非递归实现前序遍历 */    protected static void iterativePreorder(Node p) {        Stack<Node> stack = new Stack<Node>();        if (p != null) {            stack.push(p);            while (!stack.empty()) {//先右后左                p = stack.pop();                visit(p);                if (p.getRight() != null)                    stack.push(p.getRight());                if (p.getLeft() != null)                    stack.push(p.getLeft());            }        }    }    //下面高能/** 非递归实现前序遍历魔板 ********************/    protected static void iterativePreorder2(Node p) {        Stack<Node> stack = new Stack<Node>();        Node node = p;        while (node != null || stack.size() > 0) {            while (node != null) {//压入所有的左节点，压入前访问它                visit(node);                stack.push(node);                node = node.getLeft();            }            if (stack.size() > 0) {//直接只弹出栈                node = stack.pop();                node = node.getRight();            }        }    }    /** 非递归实现中序遍历魔板 **********************/    protected static void iterativeInorder2(Node p) {        Stack<Node> stack = new Stack<Node>();        Node node = p;        while (node != null || stack.size() > 0) {            while (node != null) {                stack.push(node);                node = node.getLeft();            }            if (stack.size() > 0) {                node = stack.pop();                visit(node);                node = node.getRight();            }        }    }    /** 非递归实现后序遍历魔板 ***********************/    protected static void iterativePostorderN(Node p) {        Stack<Node> stack = new Stack<Node>();        Node pre = null, node = p;        while(node!=null || stack.size()>0) {            while(node!=null) {                stack.push(node);                node = node.left;            }            node = stack.peek();            if(node.right==null || node.right == pre){                visit(node);                pre = node;                stack.pop();                node = null;            } else {                node = node.right;            }        }    }    /** 非递归实现后序遍历 */    protected static void iterativePostorder(Node p) {        Node q = p;        Stack<Node> stack = new Stack<Node>();        while (p != null) {            // 左子树入栈            for (; p.getLeft() != null; p = p.getLeft())                stack.push(p);            // 当前节点无右子或右子已经输出            while (p != null && (p.getRight() == null || p.getRight() == q)) {                visit(p);                q = p;// 记录上一个已输出节点                if (stack.empty())                    return;                p = stack.pop();            }            // 处理右子            stack.push(p);            p = p.getRight();        }    }    /** 非递归实现后序遍历 双栈法 */    protected static void iterativePostorder2(Node p) {        Stack<Node> lstack = new Stack<Node>();        Stack<Node> rstack = new Stack<Node>();        Node node = p, right;        do {            while (node != null) {                right = node.getRight();                lstack.push(node);                rstack.push(right);                node = node.getLeft();            }            node = lstack.pop();            right = rstack.pop();            if (right == null) {                visit(node);            } else {                lstack.push(node);                rstack.push(null);            }            node = right;        } while (lstack.size() > 0 || rstack.size() > 0);    }    /** 非递归实现后序遍历 单栈法*/    protected static void iterativePostorder3(Node p) {        Stack<Node> stack = new Stack<Node>();        Node node = p, prev = p;        while (node != null || stack.size() > 0) {            while (node != null) {                stack.push(node);                node = node.getLeft();            }            if (stack.size() > 0) {                Node temp = stack.peek().getRight();                if (temp == null || temp == prev) {                    node = stack.pop();                    visit(node);                    prev = node;                    node = null;                } else {                    node = temp;                }            }        }    }    /** 非递归实现后序遍历4 双栈法*/    protected static void iterativePostorder4(Node p) {        Stack<Node> stack = new Stack<Node>();        Stack<Node> temp = new Stack<Node>();        Node node = p;        while (node != null || stack.size() > 0) {            while (node != null) {                temp.push(node);                stack.push(node);                node = node.getRight();            }            if (stack.size() > 0) {                node = stack.pop();                node = node.getLeft();            }        }        while (temp.size() > 0) {            node = temp.pop();            visit(node);        }    }    /** 非递归实现中序遍历 */    protected static void iterativeInorder(Node p) {        Stack<Node> stack = new Stack<Node>();        while (p != null) {            while (p != null) {                if (p.getRight() != null)                    stack.push(p.getRight());// 当前节点右子入栈                stack.push(p);// 当前节点入栈                p = p.getLeft();            }            p = stack.pop();            while (!stack.empty() && p.getRight() == null) {                visit(p);                p = stack.pop();            }            visit(p);            if (!stack.empty())                p = stack.pop();            else                p = null;        }    }    /**     * @param args     */    public static void main(String[] args) {        BinaryTree tree = new BinaryTree(init());        System.out.print(" Pre-Order:");        preorder(tree.getRoot());        System.out.println();        System.out.print("  In-Order:");        inorder(tree.getRoot());        System.out.println();        System.out.print("Post-Order:");        postorder(tree.getRoot());        System.out.println();        System.out.print(" Pre-Order:");        iterativePreorder(tree.getRoot());        System.out.println();        System.out.print("Pre-Order2:");        iterativePreorder2(tree.getRoot());        System.out.println();        System.out.print("  In-Order:");        iterativeInorder(tree.getRoot());        System.out.println();        System.out.print(" In-Order2:");        iterativeInorder2(tree.getRoot());        System.out.println();        System.out.print(" Post-Order:");        iterativePostorder(tree.getRoot());        System.out.println();        System.out.print("Post-Order2:");        iterativePostorder2(tree.getRoot());        System.out.println();        System.out.print("Post-Order3:");        iterativePostorder3(tree.getRoot());        System.out.println();        System.out.print("Post-Order4:");        iterativePostorder4(tree.getRoot());        System.out.println();    }}