代码随想录：二叉树的所有路径

代码随想录：二叉树的所有路径

如果传入的&的话，需要在调用后进行回溯，不如直接传绝对值

/**
 * 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<string> binaryTreePaths(TreeNode* root) {
        vector<string> res;
        vector<int> path;
        tra(root, path, res);
        return res;
    }

    void tra(TreeNode* node, vector<int> path, vector<string>& res) {
        path.push_back(node->val);
        if (node->left == NULL && node->right == NULL) {
            string r = "";
            for (int i = 0; i < path.size(); i++) {
                if (i == 0) {
                    r += to_string(path[i]);
                } else {
                    r += "->";
                    r += to_string(path[i]);
                }
            }
            res.push_back(r);
        }
        if (node->left)
            tra(node->left, path, res);
        if (node->right)
            tra(node->right, path, res);
    }
};