Added solution

Author: avidLearnerInProgress

root_to_leaf_sum_binary_numbers.cpp

@@ -0,0 +1,67 @@
+/**
+ * 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:
+    void util(TreeNode *root, int &csum, int &gsum){
+        if(!root) return;      
+        csum = csum * 10 + root->val;
+        if(root->left == NULL && root->right == NULL)
+            gsum += csum;
+        util(root->left, csum, gsum);
+        util(root->right, csum, gsum);
+        csum /= 10; //once we reach one of the bottom of tree, then we start going up from root->left to root to root->right;
+    }
+    
+    int util_try(TreeNode *root, int val){
+        if(!root) return 0;
+        val = val * 10 + root->val;
+        if(!root->left && !root->right)
+            return val;
+        return util_try(root->left, val) + util_try(root->right, val);
+    }
+    
+    int util_try_iter(TreeNode *root){
+        if(!root) return 0;
+
+        queue<TreeNode*> nodeQ;
+        queue<int> sumQ;
+        nodeQ.push(root);
+        sumQ.push(root->val);
+        int gsum = 0;
+        
+        while(!nodeQ.empty()){
+            TreeNode *curr = nodeQ.front();
+            nodeQ.pop();
+            
+            int csum = sumQ.front();
+            sumQ.pop();
+            
+            if(!curr->left && !curr->right) //basecase
+                gsum += csum;
+            
+            if(curr->left){
+                nodeQ.push(curr->left); //ok..
+                sumQ.push((csum * 10) + curr->left->val); //not so ok..
+            }
+            
+            if(curr->left){
+                nodeQ.push(curr->right); //ok..
+                sumQ.push((csum * 10) + curr->right->val); //not so ok..
+            }
+        }
+        return gsum;
+    }
+    
+    int sumNumbers(TreeNode* root) {
+       if(root == NULL) return 0;
+       int csum = 0, gsum = 0;
+       return util_try(root,csum);
+    }
+};