難度中等537收藏分享切換爲英文關注反饋
給定一個二叉樹,返回它的中序 遍歷。
示例:
輸入: [1,null,2,3] 1 \ 2 / 3 輸出: [1,3,2]
進階: 遞歸算法很簡單,你可以通過迭代算法完成嗎?
/**
* 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:
vector<int> inorderTraversal(TreeNode* root)
{
vector<int> res;
if(root == nullptr) return res;
stack<TreeNode*> s;
TreeNode* cur =root;
while(cur !=NULL || !s.empty())
{
if(cur != NULL)
{
s.push(cur);
cur =cur->left;
}else{
cur = s.top();
res.push_back(cur->val);
s.pop();
cur = cur->right;
}
}
return res;
}
};