Description

Submission

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    vector<string> ret;

    void dfs(TreeNode* root, string s) {
        s += "->";
        s += to_string(root->val);
        if(!root->left && !root->right) {
            ret.push_back(s);
            return;
        }

        if(root->left) dfs(root->left, s);
        if(root->right) dfs(root->right, s);
    }
public:
    vector<string> binaryTreePaths(TreeNode* root) {
        if(root == NULL) return {};
        string s = to_string(root->val);

        if(root->left) dfs(root->left, s);
        if(root->right) dfs(root->right, s);
        if(ret.empty()) ret.push_back(s);
        
        return ret;
    }
};