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"]

二话不说，上代码：

/**
* 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> result;
if(root)
paths(root, result, to_string(root->val));

return result;
}

void paths(TreeNode* node, vector<string> &result, string str) {
if(!node->left && !node->right) {
result.push_back(str);
return;
}

if(node->left) {
paths(node->left, result, str + "->" + to_string(node->left->val));
}

if(node->right) {
paths(node->right, result, str + "->" + to_string(node->right->val));
}
}
};