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

Binary Tree Inorder Traversal.cpp

/**
 * 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
        vector<int> result;
        stack<TreeNode*> sta;
        
        if(root == NULL) {
            return result;
        }
        
        sta.push(root);
        
        while(!sta.empty()) {
            TreeNode* top = sta.top();
            if(top->left != NULL) {
                sta.push(top->left);
                top->left = NULL;
            } else {
                result.push_back(top->val);
                sta.pop();
                
                if(top->right != NULL) {
                    sta.push(top->right);
                }
            }
        }
        
        return result;
        
    }
    
    

    
};