题解 | 二叉树的后序遍历

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
class Solution {
public:
    vector<int> postorderTraversal(TreeNode* root) {
        if (root == nullptr) return {};
        vector<int> res;
        function<void(TreeNode*, vector<int>&)> dfs = [&](TreeNode* node, vector<int>& vec) {
            if (node == nullptr) return;
            dfs(node->left, vec);
            dfs(node->right, vec);
            vec.emplace_back(node->val);
        };
        dfs(root, res);
        return res;
    }
};