145.二叉树的后序遍历

::: caution

原题链接：https://leetcode.cn/problems/binary-tree-postorder-traversal/

:::

思路

根据后序遍历的定义使用递归求解。

代码

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    vector<int> res;
    void dfs(TreeNode* t) {
        if (t) {
            dfs(t->left);
            dfs(t->right);
            res.push_back(t->val);
        }
    }
    vector<int> postorderTraversal(TreeNode* root) {
        dfs(root);
        return res;
    }
};