problems(cpp): add „1448. Count Good Nodes in Binary Tree“

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/count-good-nodes-in-binary-tree.cpp

@@ -0,0 +1,28 @@
+/**
+ * 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 {
+    int goodNodes(TreeNode* root, int m)
+    {
+        if (root == nullptr) {
+            return 0;
+        }
+
+        int new_max = std::max(m, root->val);
+        return (root->val >= m) + goodNodes(root->left, new_max) + goodNodes(root->right, new_max);
+    }
+
+public:
+    int goodNodes(TreeNode* root)
+    {
+        return goodNodes(root, INT_MIN);
+    }
+};