二叉树遍历

中序递归遍历：左子树，根，右子树

    private void inOrderTraverse(Node node) {        if (node != null) {            //遍历左子树            this.inOrderTraverse(node.leftChild);            //输入根的值            System.out.print(node.value + " ");            //遍历右子树            this.inOrderTraverse(node.rightChild);        }    }

树的高度

    private int getHeight(Node node) {        if (node == null) {            return 0;        }        else {            //获取左子树高度            int lh = this.getHeight(node.leftChild);            //获取右子树高度            int rh = this.getHeight(node.rightChild);            //返回            return lh > rh ? lh + 1 : rh + 1;        }    }

树的结点数量

    private int size(Node node) {        if (node == null) {            return 0;        }        else {            int lsize = this.size(node.leftChild);            int rsize = this.size(node.rightChild);            return lsize + rsize + 1;        }    }

树档次遍历：借助队列

public void levelOrderByStack() {        if (root == null) return;        Queue<Node> queue = new LinkedList<Node>();        queue.add(root);        while (queue.size() != 0){            for (int i = 0; i < queue.size(); i++) {                //取出以后队列中的结点                Node temp = queue.poll();                //打印一下结点的值                System.out.print(temp.value+"--");                //把该结点的左子树加到队列中                if (temp.leftChild != null)                    queue.add(temp.leftChild);                //把右子树加到队列中                if (temp.rightChild != null)                    queue.add(temp.rightChild);            }        }    }

中序遍历 非递归

public void inOrderByStack() {        Deque<Node> stack = new LinkedList<>();        Node current = root;        while (current != null || !stack.isEmpty()){            while (current != null){                stack.push(current);                current = current.leftChild;            }            if(!stack.isEmpty()){                current = stack.pop();                System.out.println(current.value+" ");                current = current.rightChild;            }        }    }