Easy one of LeetCode

Binary Inorder Traversal

class Solution {
public:
    vector<int> inorderTraversal(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> solTree;
        if (root == NULL) {
            //solTree.push_back(NULL);
            return solTree;
        }
       
        if (root->left) {
            vector<int> leftTree;
            leftTree = inorderTraversal(root->left);
            solTree = leftTree;
        }
        solTree.push_back(root->val);
        if (root->right) {
            vector<int> rightTree;
            rightTree = inorderTraversal(root->right);
            solTree.insert(solTree.end(), rightTree.begin(), rightTree.end());
        }
        return solTree;
    }
};