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.
For example,
1
/ \
2 3
The root-to-leaf path 1->2 represents the number 12. The root-to-leaf path 1->3 represents the number 13.
Return the sum = 12 + 13 = 25.
Solution:
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int sumNumbers(TreeNode root) {
return sumNumbers(root, 0);
}
public int sumNumbers(TreeNode root, int sum) {
if(root==null) return 0;
if(root.left==null && root.right==null) return sum*10+root.val;
else return sumNumbers(root.left, sum*10+root.val) + sumNumbers(root.right, sum*10+root.val);
}
}