### LeetCode Challenge #1372. Longest ZigZag Path in a Binary Tree

You are given the `root` of a binary tree.

A ZigZag path for a binary tree is defined as follow:

• Choose any node in the binary tree and a direction (right or left).
• If the current direction is right, move to the right child of the current node; otherwise, move to the left child.
• Change the direction from right to left or from left to right.
• Repeat the second and third steps until you can’t move in the tree.

Zigzag length is defined as the number of nodes visited – 1. (A single node has a length of 0).

Return the longest ZigZag path contained in that tree.

Example 1:

```Input: root = [1,null,1,1,1,null,null,1,1,null,1,null,null,null,1]
Output: 3
Explanation: Longest ZigZag path in blue nodes (right -> left -> right).
```

Example 2:

```Input: root = [1,1,1,null,1,null,null,1,1,null,1]
Output: 4
Explanation: Longest ZigZag path in blue nodes (left -> right -> left -> right).
```

Example 3:

```Input: root = [1]
Output: 0
```

Constraints:

• The number of nodes in the tree is in the range `[1, 5 * 104]`.
• `1 <= Node.val <= 100`
##### Video Solution
###### C++ Solution
```				```
class Solution {
public:
int maxm=0;

void zigzag(TreeNode* root, bool right,int count)
{
if(!root)
{
maxm=max(maxm,count-1);
return;
}

if(!right) zigzag(root->right,true,count+1);
else zigzag(root->left,false,count+1);

}

void dfs(TreeNode*root)
{
if(root==NULL)return;
zigzag(root,true,0);
zigzag(root,false,0);
dfs(root->left);
dfs(root->right);
}

int longestZigZag(TreeNode* root) {
if(!root || (!root->left and !root->right))return 0;
dfs(root);
return maxm;
}
};
```
```