leetcode题解（四十三）：114. Flatten Binary Tree to Linked List

把二叉树变成链表

看图片应该是前序遍历

private TreeNode prev = null;

public void flatten(TreeNode root) {
    if (root == null)
        return;
    flatten(root.right);
    flatten(root.left);
    root.right = prev;
    root.left = null;
    prev = root;
}