Sum Root to Leaf Numbers Solution.cpp

PROBLEM:


Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.
An example is the root-to-leaf path 1->2->3 which represents the number 123.
Find the total sum of all root-to-leaf numbers.

Note: A leaf is a node with no children.

Example:
Input: [1,2,3]
    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:
Input: [4,9,0,5,1]
    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.




SOLUTION:



/**
 * 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:
    void inorder(TreeNode *root,int& s)
    {
        if(root==NULL)
            return;
        
        if(root->left!=NULL)
        {   
            root->left->val+=(root->val)*10;
            inorder(root->left,s);
        }
        
        if(root->right!=NULL)
        {   
            root->right->val+=(root->val)*10;
            inorder(root->right,s);
        }
        
        if(root->left==NULL && root->right==NULL)
            s+=root->val;
    }
    
    int sumNumbers(TreeNode* root) {
        
        if(root==NULL)
            return 0;
        
        int s=0;
        
        inorder(root,s);
       
        return s;
    }  
};