Create sum-of-root-to-leaf-binary-numbers.cpp

Author: kamyu104

C++/sum-of-root-to-leaf-binary-numbers.cpp

@@ -0,0 +1,32 @@
+// 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 sumRootToLeaf(TreeNode* root) {
+        return sumRootToLeafHelper(root, 0);
+    }
+
+private:
+    int sumRootToLeafHelper(TreeNode* root, int val) {
+        static const int M = 1e9 + 7;
+        if (!root) {
+            return 0;
+        }
+        val = (val * 2 + root->val) % M;
+        if (!root->left && !root->right) {
+            return val;
+        }
+        return (sumRootToLeafHelper(root->left, val) +
+                sumRootToLeafHelper(root->right, val)) % M;
+    }
+};