Morris遍历

Morris遍历二叉树
前序遍历

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public List<Integer> preorderTraversal(TreeNode root) {
        List<Integer> res=new ArrayList<>();
        if(root==null){
            return res;
        }
        TreeNode cur=root;
        TreeNode mostRight=null;
        while(cur!=null){
            mostRight=cur.left;
            if(mostRight!=null){
                while(mostRight.right!=null&&mostRight.right!=cur){
                    mostRight=mostRight.right;
                }
                if(mostRight.right==null){
                    res.add(cur.val);
                    mostRight.right=cur;
                    cur=cur.left;
                    continue;
                }else{
                    mostRight.right=null;
                }
            }else{
                res.add(cur.val);
            }
            cur=cur.right;
        }
        return res;
    }
}

中序遍历

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public List<Integer> inorderTraversal(TreeNode root) {
        List<Integer> res=new ArrayList<>();
        if(root==null){
            return res;
        }
        TreeNode cur=root;
        TreeNode mostRight=null;
        while(cur!=null){
            mostRight=cur.left;
            if(mostRight!=null){
                while(mostRight.right!=null&&mostRight.right!=cur){
                    mostRight=mostRight.right;
                }
                if(mostRight.right==null){
                    mostRight.right=cur;
                    cur=cur.left;
                    continue;
                }else{
                    res.add(cur.val);
                    mostRight.right=null;
                }
            }else{
                res.add(cur.val);
            }
            cur=cur.right;
        }
        return res;
    }
}