257. Binary Tree Paths.cpp

/*
Given the root of a binary tree, return all root-to-leaf paths in any order.
A leaf is a node with no children.

Example 1:
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 [1, 100].
-100 <= Node.val <= 100
*/ 
/**
 * 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:
    void binaryTreePaths(vector<string>& result, TreeNode* root, string t) {
        if(!root->left && !root->right) {
            result.push_back(t);
            return;
        }
        if(root->left) binaryTreePaths(result, root->left, t + "->" + to_string(root->left->val));
        if(root->right) binaryTreePaths(result, root->right, t + "->" + to_string(root->right->val));
    }
    
    vector<string> binaryTreePaths(TreeNode* root) {
        vector<string> result;
        if(!root) return result;

        binaryTreePaths(result, root, to_string(root->val));
        return result;
    }
};