ADD sum of root to leaf binary algorithm

Author: Alex0Blackwell

Algorithms/sumOfRootToLeafBinary.cpp

@@ -0,0 +1,34 @@
+/**
+ * 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 rootToLeaf = 0;
+
+    void preorder(TreeNode* curr, int currNumber) {
+        if(curr == nullptr)
+            return;
+        currNumber = (currNumber << 1) | curr->val;
+
+        if(curr->left == nullptr && curr->right == nullptr)
+            rootToLeaf += currNumber;
+
+        preorder(curr->left, currNumber);
+        preorder(curr->right, currNumber);
+    }
+
+
+    int sumRootToLeaf(TreeNode* root) {
+        preorder(root, 0);
+
+        return rootToLeaf;
+    }
+};

README.md

@@ -159,6 +159,9 @@ Click to expand the 43 *C++ programs*!
   - sumNodesEvenGrandparent.cpp
     - Given a binary tree, return the sum of values of nodes with even-valued grandparent.  (A grandparent of a node is the parent of its parent, if it exists.) If there are no nodes with an even-valued grandparent, return 0.
     - Leetcode problem found [here](https://leetcode.com/problems/sum-of-nodes-with-even-valued-grandparent/)
+  - sumOfRootToLeafBinary.cpp
+    - You are given the root of a binary tree where each node has a value 0 or 1.  Each root-to-leaf path represents a binary number starting with the most significant bit.  For example, if the path is 0 -> 1 -> 1 -> 0 -> 1, then this could represent 01101 in binary, which is 13.
+    - Leetcode problem found [here](https://leetcode.com/problems/sum-of-root-to-leaf-binary-numbers/)
   - toLowerCase.cpp
     - Implement function ToLowerCase() that has a string parameter str, and returns the same string in lowercase.
   - word2num.cpp