LeetCode 114 Flatten Binary Tree to Linked List

题目描述

Given a binary tree, flatten it to a linked list in-place.

For example,

Given



The flattened tree should look like:

代码

[code]    TreeNode prev;

    void preorder(TreeNode root) {

        if (root == null)
            return;

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

        // root
        if (prev != null) {
            prev.right = root;
            prev.left = null;
        }

        prev = root;

        preorder(left);
        preorder(right);
    }

    public void flatten(TreeNode root) {
        prev = null;
        preorder(root);
    }