257. Binary Tree Paths

[namespace-io]

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;
}

/**
 * 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 {
public:
    
    void dfs(TreeNode* root, string& path, vector<string>& v){
        auto t = path;
        path += "->" + to_string(root->val);
        if(root->left == nullptr && root->right == nullptr){
            v.push_back(path);
        }
        if(root->left != nullptr){
            dfs(root->left, path, v); 
        } 
        
        if(root->right != nullptr){

            dfs(root->right, path, v);
        } 
        
        path = t;
    }
    
    vector<string> binaryTreePaths(TreeNode* root) {
        vector<string> v;
        if(root == nullptr) return v;
        
        string path = to_string(root->val);
        if(root->left == nullptr && root->right == nullptr) v.push_back(path);
        if(root->left) dfs(root->left, path, v);
        if(root->right) dfs(root->right, path, v);
        
        return v;
    }
};