day_08.cpp

/*PROBLEM STATEMENT:
For all leaves in the tree, consider the numbers represented by the path from the root to that leaf.

Return the sum of these numbers.

Example 1:
             1
          /    \
         0      1
       /   \   /  \
      0     1 0     1
      
Input: [1,0,1,0,1,0,1]
Output: 22
Explanation: (100) + (101) + (110) + (111) = 4 + 5 + 6 + 7 = 22

*/

//CODE:

/*
 * 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 {
    int sumRootToLeaf(TreeNode* root,int sum){
        if(!root) return 0;
        sum = (sum << 1) + root->val;
        //checks if the node is leaf or not
        if(!root->left && !root->right) return sum;
        return sumRootToLeaf(root->left, sum) + sumRootToLeaf(root->right, sum);
    }
public:
    int sumRootToLeaf(TreeNode* root) {
        return sumRootToLeaf(root,0);
    }
};