1448. Count Good Nodes in Binary Tree.cpp

/**
 * 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 goodNodes(TreeNode* root) {
        int res=0;
        dfs(root,root->val,res);
        return res;
    }
    void dfs(TreeNode* root,int maxi,int& res){
        if(!root) return;
        if(root->val >= maxi) res++;
        dfs(root->left,max(maxi,root->val),res); 
        dfs(root->right,max(maxi,root->val),res); 
    }
};