leetcode114
程序代码：struct TreeNode {
int val;
TreeNode *left;
TreeNode *right;
TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};
class Solution {
public:
void flatten(TreeNode* root) {//后序遍历；
if(root==NULL)return;
flatten(root->left);
flatten(root->right);
TreeNode *temp=root->right;
root->right=root->left;
root->left=NULL;
while(root->right)root=root->right;
root->right=temp;
}
};
while那行改变了root，root不就不是头结点了吗，这么做为什么没有问题？
