Flatten Binary Tree to Linked List

標籤：java   leetcode   tree   

題目

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

For example,
Given

         1        /        2   5      / \        3   4   6

The flattened tree should look like:

   1         2             3                 4                     5                         6

方法

先將根節點的左子樹串連到右邊，在遞迴處理子節點。

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