LeetCode：114二叉树展开为链表

/**
 * 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) {
        TreeNode curr = root;

        while(curr != null){
            //只有左子树存在的时候才需要移接
            if(curr.left != null){
                //在左子树中找最右下角节点
                TreeNode pre = curr.left;
                while(pre.right != null){
                    pre = pre.right;
                }

                pre.right = curr.right;

                curr.right = curr.left;
                curr.left = null;
            }
            curr = curr.right;
        }
    }
}

做的过程中对照代码画图更好理解。