LeetCode 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"]

代码

/**
 * 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) {
        vector<string> results;
        vector<int> path;
        binaryTreePaths(root, path, results);
        return results;
    }
    void binaryTreePaths(TreeNode* root, vector<int> path, vector<string>& results){
        if(root == NULL){
            //Error
            return;
        }
        path.push_back(root->val);
        if(root->left == NULL && root->right == NULL) {
            //Leaf
            string result;
            int pSize = path.size();
            for(int i=0; i<pSize; i++){
                result += to_string(path[i]);
                if(i != pSize - 1)
                    result += "->";
            }
            results.push_back(result);
        } else {
            if(root->left != NULL)
                binaryTreePaths(root->left, path, results);
            if(root->right != NULL)
                binaryTreePaths(root->right, path, results);
        }
    }
};