Create sum-of-nodes-with-even-valued-grandparent.cpp

Author: kamyu104

Diff for: C++/sum-of-nodes-with-even-valued-grandparent.cpp

@@ -0,0 +1,27 @@
+// Time:  O(n)
+// Space: O(h)
+
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    int sumEvenGrandparent(TreeNode* root) {
+        return sumEvenGrandparentHelper(root, 1, 1);
+    }
+
+private:
+    int sumEvenGrandparentHelper(TreeNode *root, int p, int gp) {
+        return root
+               ? sumEvenGrandparentHelper(root->left, root->val, p) +
+                 sumEvenGrandparentHelper(root->right, root->val, p) +
+                 (gp % 2 == 0 ? root->val : 0)
+               : 0;
+    }
+};