1372. Longest ZigZag Path in a Binary Tree

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
int cnt=0;
int sol(TreeNode* root, bool dir){
    if(root==NULL)return 0;
    int left=0,right=0;
    if(root->right){
         right=1+sol(root->right,false);
    }
    if(root->left){
         left=1+sol(root->left,true);
    }
    cnt=max({left,right,cnt});
    if(dir==false)return left;
    else return right;
}

    int longestZigZag(TreeNode* root) {
        sol(root,false);
        return cnt;
    }
};