# Sum Root To Leaf Numbers Problem

## Description

LeetCode Problem 129.

You are given the root of a binary tree containing digits from 0 to 9 only.

Each root-to-leaf path in the tree represents a number.

• For example, the root-to-leaf path 1 -> 2 -> 3 represents the number 123.

Return the total sum of all root-to-leaf numbers. Test cases are generated so that the answer will fit in a 32-bit integer.

A leaf node is a node with no children.

Example 1:

``````1
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Input: root = [1,2,3]
Output: 25
Explanation:
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.
Therefore, sum = 12 + 13 = 25.
``````

Example 2:

``````1
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Input: root = [4,9,0,5,1]
Output: 1026
Explanation:
The root-to-leaf path 4->9->5 represents the number 495.
The root-to-leaf path 4->9->1 represents the number 491.
The root-to-leaf path 4->0 represents the number 40.
Therefore, sum = 495 + 491 + 40 = 1026.
``````

Constraints:

• The number of nodes in the tree is in the range [1, 1000].
• 0 <= Node.val <= 9
• The depth of the tree will not exceed 10.

## Sample C++ Code

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class Solution {
public:
int sumNum(TreeNode* root, int num) {
if (root == NULL)
return num;
int curr = num * 10 + root->val;
int sum = 0;
if (root->left != NULL)
sum += sumNum(root->left, curr);
if (root->right != NULL)
sum += sumNum(root->right, curr);
if ((root->left == NULL) && (root->right == NULL))
sum += curr;
return sum;
}
int sumNumbers(TreeNode* root) {
return sumNum(root, 0);
}
};
``````