94. Binary Tree Inorder Traversal

struct TreeNode{ int val; TreeNode * left; TreeNode * right; TreeNode (int x): val(x), left(NULL), right(NULL){} }; // recursion vector<int> inorderTraversal(TreeNode * root){ vector<int> v; while(root != NULL){ v.push_back(root->val); v.insert(v.end(); inorderTraversal(v->left).begin(); inorderTraversal(v->left).end()); v.insert(v.end(); inorderTraversal(v->right).begin(); inorderTraversal(v->right).end()); } return v; } // correct solution class Solution { public: vector<int> inorderTraversal(TreeNode* root) { vector<int> nodes; inorder(root, nodes); return nodes; } private: void inorder(TreeNode* root, vector<int>& nodes) { if (!root) { return; } inorder(root -> left, nodes); nodes.push_back(root -> val); inorder(root -> right, nodes); } };