257. Binary Tree Paths

Given a binary tree, return all root-to-leaf paths.

For example, given the following binary tree:

 

   1
 /   
2     3
 
  5

 

All root-to-leaf paths are:

["1->2->5", "1->3"]

输出所有根节点到叶子节点的路径

C++(6ms):

/**
 * 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 binaryTreePaths(vector<string>& res ,TreeNode* root , string t) {
        if (!root->left && !root->right){
            res.push_back(t) ;
            return ;
        }
        if (root->left) binaryTreePaths(res,root->left,t + "->" + to_string(root->left->val)) ;
        if (root->right) binaryTreePaths(res,root->right,t + "->" + to_string(root->right->val)) ;
    }
        
    vector<string> binaryTreePaths(TreeNode* root) {
        vector<string> res ;
        if (!root)
            return res ;
        binaryTreePaths(res,root,to_string(root->val)) ;
        return res ;
    }
};