LeetCode *** 257. Binary Tree Paths

题目：
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"]

分析：
用dfs即可。

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> res;

stack<TreeNode*> tree;
stack<string> tmpR;

if(root){
tree.push(root);
tmpR.push(to_string(root->val));
}

while(!tree.empty()){
TreeNode *tmpNode=tree.top();
string tmp=tmpR.top();
tree.pop();
tmpR.pop();

if(tmpNode->left==NULL&&tmpNode->right==NULL)
res.push_back(tmp);

if(tmpNode->right){
tree.push(tmpNode->right);
tmpR.push(tmp+"->"+to_string(tmpNode->right->val));
}

if(tmpNode->left){
tree.push(tmpNode->left);
tmpR.push(tmp+"->"+to_string(tmpNode->left->val));
}
}

return res;
}
};