Create maximum-average-subtree.cpp

Author: kamyu104

C++/maximum-average-subtree.cpp

@@ -0,0 +1,33 @@
+// 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:
+    double maximumAverageSubtree(TreeNode* root) {
+        double result = 0.0;
+        maximumAverageSubtreeHelper(root, &result);
+        return result;
+    }
+
+private:
+    pair<double, double> maximumAverageSubtreeHelper(TreeNode *root, double *result) {
+        if (!root) {
+            return {0, 0};
+        }
+        const auto& [s1, n1] = maximumAverageSubtreeHelper(root->left, result);
+        const auto& [s2, n2] = maximumAverageSubtreeHelper(root->right, result);
+        const auto& s = s1 + s2 + root->val;
+        const auto& n = n1 + n2 + 1;
+        *result = max(*result, s / n);
+        return {s, n};
+    }
+};