二叉树的先序遍历—非递归

https://github.com/yuanoOo/Algorithm/tree/master/BinaryTree/%E9%81%8D%E5%8E%86%E4%BA%8C%E5%8F%89%E6%A0%91

递归先序遍历

    /**
     * 递归的方法实现先序遍历二叉树
     */
    public static void printBinaryTreeRecursive(Node node){
        if (node == null)
            return;

        System.out.println(node.value + " ");
        printBinaryTreeRecursive(node.left);
        printBinaryTreeRecursive(node.right);
    }

非递归先序遍历

image.png

/**
     * 非递归方法实现先序遍历二叉树
     */
    public static void printBinaryTree(Node node){
        //工程方面不要使用Stack，这是java中过时的api，DeQueue是一个更好的选择
        Stack<Node> stack = new Stack<>();// only for convenient

        Node current = null;
        //1.将头节点head压入stack中
        stack.push(node);
        while (!stack.isEmpty()){
            current = stack.pop();
            System.out.print(current.value + " ");

            if (current.right != null) stack.push(current.right);
            if (current.left != null) stack.push(current.left);
        }
    }