day49（12.30）——leetcode面试经典150

114. 二叉树展开为链表

114. 二叉树展开为链表

题目：

题解：

/**
 * 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) {
        while(root != null) {
            //左子树为null,直接考虑下一节点
            if(root.left == null) {
                root = root.right;
            }
            else {
                //找到左子树最右边的结点
                TreeNode pre = root.left;
                while(pre.right != null) {
                    pre = pre.right;
                }
                //将原来的右子树接到左子树的最右边结点
                pre.right = root.right;
                root.right = root.left;
                root.left = null;
                root = root.right;
            }
        }
    }
}