//二叉樹遍歷
/*
 * 前序遍歷：根左右
 * 中序遍歷：左根右
 * 後序遍歷：左右根
 * 層序遍歷：從上往下、從左往右
 *
 * 遞迴遍歷：使用遞迴方法遍歷
 * 迭代遍歷：使用迭代方法實現遞迴函式，與遞迴等價
 * morris遍歷
 * */
public class P28 {

    /*
    *           1
    *         /   \
    *       2       3
    *     /   \
    *   4       5
    *         /   \
    *       6       7
    * */
    public
 
 static void main(String[] args) {
        TreeNode node7 = new TreeNode(7, null, null);
        TreeNode node6 = new TreeNode(6, null, null);
        TreeNode node5 = new TreeNode(5, node6, node7);
        TreeNode node4 = new TreeNode(4, null, null);
        TreeNode node3 = new TreeNode(3, null, null
 
);
        TreeNode node2 = new TreeNode(2, node4, node5);
        TreeNode node1 = new TreeNode(1, node2, node3);

        iter(node1);
    }

    //中序-迭代
    //4-2-6-5-7-1-3
    public static void iter(TreeNode root){

        if(root != null){
            Stack<TreeNode> stack = new Stack<>();
            
 
while(!stack.isEmpty() || root != null){
                if(root != null){
                    stack.push(root);       //不停讓左節點進棧
                    root = root.left;
                }else{          //知道左節點是null
                    root = stack.pop();         //變回父節點
                    System.out.println(root.val);   //輸出父節點
                    root = root.right;          //開始右邊孩子
                }
            }
        }
    }

    static class TreeNode{
        int val;
        TreeNode left;
        TreeNode right;
        int deep;

        TreeNode(){}

        TreeNode(int val){
            this.val = val;
        }

        TreeNode(int val, TreeNode left, TreeNode right){
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }

}