leetcode 94.Binary Tree Inorder Traversal 二叉树的中序遍历

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     vector<int> inorderTraversal(TreeNode* root) {
13         vector<int> tra;
14         Morder(root,tra);
15         return tra;
16     }
17     void Morder(TreeNode* root,vector<int> &tra){
18         if(root==NULL) return;
19         if(root->left)
20             Morder(root->left,tra);
21         tra.push_back(root->val);
22         if(root->right)
23             Morder(root->right,tra);
24     }
25 };

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     vector<int> inorderTraversal(TreeNode* root) {
13         //使用栈的非递归方法
14         vector<int> res;
15         stack<TreeNode*> st;
16         TreeNode* T=root;
17         while(T||!st.empty()){
18             //将T的所有左孩子入栈
19             while(T){
20                 st.push(T);
21                 T=T->left;
22             }
23             //访问T的元素，然后转到T的右孩子
24             if(!st.empty()){
25                 T=st.top();
26                 st.pop();
27                 res.push_back(T->val);
28                 T=T->right;
29             }
30         }
31         return res;
32     }
33 };