java 二叉树的递归遍历和非递归遍历-优快云博客

本文链接：https://blog.youkuaiyun.com/olpf1128/article/details/76828437

本文介绍了二叉树的前序、中序和后序遍历算法及其基于栈的实现方式，通过递归和非递归两种方法展示了如何访问二叉树中的节点。

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    //root left right
    public void preTrace(Node rootNode){
        if(rootNode != null){
            System.out.print(rootNode.data+",");
            preTrace(rootNode.left);
            preTrace(rootNode.right);
        }
    }

    public void preStackTrace(Node root){
        TreeStack stack = new TreeStack(30);
        stack.push(root);
        System.out.println("preTraceStack");
        while(!stack.isEmpty()){
            Node tmp = stack.pop();
            System.out.print(tmp.data+",");
            if(tmp.right != null)
                stack.push(tmp.right);
            if(tmp.left != null)
                stack.push(tmp.left);
        }
        System.out.println();
    }

    // left root right
    public void midTrace(Node rootNode){
        if(rootNode != null){
            midTrace(rootNode.left);
            System.out.print(rootNode.data+",");
            midTrace(rootNode.right);
        }
    }

    public void midStackTrace(Node root){
        TreeStack stack = new TreeStack(30);

        Node cur = root;
        System.out.println("midTraceStack");
        while(cur != null || !stack.isEmpty()){
            while(cur != null){
                stack.push(cur);
                cur = cur.left;
            }
            if(!stack.isEmpty()){
                cur = stack.pop();
                System.out.print(cur.data+",");
                cur = cur.right;
            }
        }
        System.out.println();
    }

    //left right root
    public void backTrace(Node rootNode){
        if(rootNode != null){
            backTrace(rootNode.left);
            backTrace(rootNode.right);
            System.out.print(rootNode.data+",");
        }
    }

    public void backStackTrace(Node root){
        System.out.println("backTraceStack:");
        TreeStack stack = new TreeStack(30);
        stack.push(root);
        Node cur = root.left;
        Node last;
        while(!stack.isEmpty()) {
            while(cur != null){
                stack.push(cur);
                cur = cur.left;
            }
            if(stack.peek().right == null){
                System.out.print(stack.peek().data+",");
                last = stack.pop();
                if(stack.isEmpty())
                    break;
                if(last == stack.peek().right){
                    stack.peek().right = null;
                }
            }
            cur = stack.peek().right;
        }
        System.out.println();
    }