leetcode 94 中序遍历模板

/**递归的写法
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
 void MiddleTravel(TreeNode * root,vector<int>&result_vec) {
        if(root!=NULL) {
            MiddleTravel(root->left,result_vec);
            result_vec.push_back(root->val);
            MiddleTravel(root->right,result_vec);
        }
 }
class Solution {
public:
    vector<int> inorderTraversal(TreeNode* root) {
        vector<int>result_vec;
        MiddleTravel(root,result_vec);
        return result_vec;
    }
};
下面是一个不用递归的写法，用栈：

 /**
  * 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>result_vec;
         stack<TreeNode *>q_stack;
         TreeNode *NowNode=root;
         while(NowNode||!q_stack.empty()) {
             if(NowNode!=NULL) {
                 q_stack.push(NowNode);
                 NowNode=NowNode->left;
             }
             else {
                 NowNode=q_stack.top();
                 result_vec.push_back(NowNode->val);
                 q_stack.pop();
                 NowNode=NowNode->right;
             }
         }
         return result_vec;
     }
 };