[LeetCode] 94. Binary Tree Inorder Traversal (C++)

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[LeetCode] 94. Binary Tree Inorder Traversal (C++)

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

Example:

Input: [1,null,2,3]
1

2
/
3

Output: [1,3,2]
Follow up: Recursive solution is trivial, could you do it iteratively?

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */


/* Recursive implementation */
class Solution {
public:
    vector<int> inorderTraversal(TreeNode* root) {
        vector<int> res;
        IOT(root,res);
        return res;
    }
    
    void IOT(TreeNode* root,vector<int> &r) {
        if(root) {
            IOT(root->left,r);
            r.push_back(root->val);
            IOT(root->right,r);
        }
    }
};


/**
 * Submission Detail:
 * Runtime: 4 ms, faster than 100.00% of C++ online submissions for Binary Tree Inorder Traversal.
 * Memory Usage: 9.5 MB, less than 15.33% of C++ online submissions for Binary Tree Inorder Traversal.
*/