LeetCode 257. 二叉树的所有路径

给定一个二叉树，返回所有从根节点到叶子节点的路径。

说明: 叶子节点是指没有子节点的节点。

示例:

输入:

   1
 /   \
2     3
 \
  5

输出: ["1->2->5", "1->3"]

解释: 所有根节点到叶子节点的路径为: 1->2->5, 1->3

 

/**
 * 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:
    vector<string> binaryTreePaths(TreeNode* root) {
        if (root == NULL)
            return {};

        vector<string> leftPaths = binaryTreePaths(root->left);
        vector<string> rightPaths = binaryTreePaths(root->right);

        vector<string> paths;
        for (auto p: leftPaths)
            paths.push_back(to_string(root->val) + "->" + p);
        for (auto p: rightPaths)
            paths.push_back(to_string(root->val) + "->" + p);
        if (paths.empty())
            paths.push_back(to_string(root->val));
        return paths;
    }
};