Binary Tree Paths

Description:

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"]

Code:

  void allPath(TreeNode*root, vector<string>&result, vector<int>&path)
    {
        if (root==NULL)
            return ;
        path.push_back(root->val);
        if (root->left==NULL && root->right==NULL)
        {
//注意这里要用ostringstream将字符串写到流中去，然后用str（）函数返回字符串
            ostringstream sstr;
            for (int i = 0; i < path.size()-1; ++i)
                sstr << path[i]<<"->";
            sstr<<path[path.size()-1];
            result.push_back(sstr.str());
        }
        else
        {
            if (root->left)
                allPath(root->left, result, path);
            if (root->right)
                allPath(root->right, result, path);
        }
        path.pop_back();
    }
    vector<string> binaryTreePaths(TreeNode* root) {
        vector<string>result;
        vector<int>path;
        allPath(root, result,path);
        return result;
    }