leetcode-二叉树展开为链表

//leetcode submit region begin(Prohibit modification and deletion)

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 * int val;
 * TreeNode left;
 * TreeNode right;
 * TreeNode() {}
 * TreeNode(int val) { this.val = val; }
 * TreeNode(int val, TreeNode left, TreeNode right) {
 * this.val = val;
 * this.left = left;
 * this.right = right;
 * }
 * }
 */
class Solution {
    public void flatten(TreeNode root) {
        if (root == null) {
            return;
        }
        flatten(root.left);
        flatten(root.right);


        TreeNode left = root.left;
        TreeNode right = root.right;


        root.left = null;
        root.right = left;

        TreeNode p = root;
        while (p.right!=null) {
            System.out.println(p.val);
            p = p.right;
        }
        p.right = right;
    }
}
//leetcode submit region end(Prohibit modification and deletion)