leetcode

0 class Solution {

1 int res = 0;

2

3 int dfs(TreeNode *root, bool zig) {

4 if (!root) return -1;

5

6 int left = dfs(root->left, false);

7 int right = dfs(root->right, true);

8 res = max(res, max(left + 1, right + 1));

9

10 return zig ? left + 1 : right + 1;

11 }

12

13 public:

14 int longestZigZag(TreeNode *root) {

15 dfs(root, false);

16 return res;

17 }

18 };