递归,让last节点指向遍历的节点。
/**
* 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:
TreeNode* last = nullptr;
void flatten(TreeNode* root) {
recursive(root);
}
void recursive(TreeNode* root){
if(!root) return;
if(last){
last->left = nullptr;
last->right = root;
}
last = root;
TreeNode* rightTemp = root->right;
recursive(root->left);
recursive(rightTemp);
}
};