给定一个二叉树,返回它的中序 遍历。
示例:
输入: [1,null,2,3]
1
\
2
/
3
输出: [1,3,2]
进阶: 递归算法很简单,你可以通过迭代算法完成吗?
/**
* 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> result;
void LDR(TreeNode* root)
{
if(root==NULL)
return;
LDR(root->left);
result.push_back(root->val);
LDR(root->right);
}
vector<int> inorderTraversal(TreeNode* root) {
LDR(root);
return result;
}
};
递归方法
/**
* 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) {
stack<TreeNode*> s;
TreeNode *p=root;
vector<int> result;
while(p!==NULL||!s.empty()){
while(p!=NULL){
s.push(p);
p=p->left;
}
if(!s.empty()){
p=s.top();
result.push_back(p->val);
s.pop();
p=p->right;
}
}
return result;
}
迭代方法