[leetcode]Binary Tree Inorder Traversal

Given a binary tree, return the inorder traversal of its nodes' values.

For example:
Given binary tree {1,#,2,3},

   1
    
     2
    /
   3

 

return [1,3,2].

Note: Recursive solution is trivial, could you do it iteratively?

一次通过~~ 耶

 

/**
 * Definition for binary tree
 * 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) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if(!root) return vector<int>();
        
        vector<int> result;
        stack<pair<TreeNode*, bool>> s;
        s.push(pair<TreeNode*, bool>(root, false));
        
        TreeNode *curNode;
        bool curFlag;
        
        while(!s.empty()){
            curNode = s.top().first;
            curFlag = s.top().second;
            s.pop();
            
            if(curFlag){
                //second access
                result.push_back(curNode->val);
            }else{
                //first access, push right, self, left
                if(curNode -> right) s.push(pair<TreeNode*, bool>(curNode->right, false));
                s.push(pair<TreeNode*, bool>(curNode, true));
                if(curNode -> left) s.push(pair<TreeNode*, bool>(curNode->left, false));
                
            }
            
        }
        
        return result;
        
    }
};