LeetCode:Binary Tree Inorder Traversal

Binary Tree Inorder Traversal

Total Accepted: 126544  Total Submissions: 316559  Difficulty: Medium

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?

confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.

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c++ code:

/**
 * 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 inorderTraversal(TreeNode* root) {
        vector ivec;
        TreeNode *p=root;
        stack s;
        while(p || !s.empty()){
            while(p){
                s.push(p);
                p=p->left;
            }
            if(!s.empty()){
                p=s.top();
                ivec.push_back(p->val);
                s.pop();
                p=p->right;
            }
        }
        return ivec;
    }
};