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"]

Credits:

Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

//简单的二叉树遍历，遍历的过程中记录之前的路径，一旦遍历到叶子节点便将该路径增加结果中。
class Solution {
public:
	vector<string> binaryTreePaths(TreeNode* root) {
		vector<string> res;
		if (root==NULL)   return res;
		binaryTreePaths(res, root, to_string(root->val));
		return res;
	}

	void binaryTreePaths(vector<string>& result, TreeNode* node, string s) {
		if (node->left==NULL && node->right==NULL)
		{
			result.push_back(s);
			return;
		}
		if (node->left)     binaryTreePaths(result, node->left, s + "->" + to_string(node->left->val));
		if (node->right)    binaryTreePaths(result, node->right, s + "->" + to_string(node->right->val));
	}
};