# LC 257. Binary Tree Paths

### [Problem link](https://leetcode.com/problems/binary-tree-paths/)

###### tags: `leedcode` `easy` `c++` `Binary Tree`

Given the <code>root</code> of a binary tree, return all root-to-leaf paths in **any order** .

A **leaf** is a node with no children.

**Example 1:**
<img alt="" src="https://assets.leetcode.com/uploads/2021/03/12/paths-tree.jpg" style="width: 207px; height: 293px;" />

Input: root = [1,2,3,null,5]
Output: ["1->2->5","1->3"]

**Example 2:**

Input: root = [1]
Output: ["1"]

**Constraints:**

- The number of nodes in the tree is in the range <code>[1, 100]</code>.
- <code>-100 <= Node.val <= 100</code>

## Solution 1
#### C++

class Solution {
public:
    vector<string> res;

    void traversal(TreeNode *node, string path) {
        path += to_string(node->val);
        if (node->left == nullptr && node->right == nullptr) {
            res.push_back(path);
        }
        if (node->left != nullptr) {
            traversal(node->left, path + "->");
        }
        if (node->right != nullptr) {
            traversal(node->right, path+ "->");
        }
    }

    vector<string> binaryTreePaths(TreeNode* root) {
        string path;

        if (root == nullptr) {
            return res;
        }
        traversal(root, path);
        return res;
    }
};

>### Complexity
>| | Time Complexity | Space Complexity |
>| ----------- | --------------- | ---------------- |
>| Solution 1 | O(n) | O(1) |

## Note
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