LeetCode 114. 二叉树展开为链表

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void flatten(TreeNode* root) {
        auto now=root;
        while(now){
            if(now->left){
                auto p=now->left;
                while(p->right)p=p->right;
                p->right=now->right;
                now->right=now->left;
                now->left=NULL;
            }
            now=now->right;
        }
    }
};