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.
A leaf is a node with no children.Have you met this question in a real interview? Yes
Example
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.
/**
* Definition of TreeNode:
* public class TreeNode {
* public int val;
* public TreeNode left, right;
* public TreeNode(int val) {
* this.val = val;
* this.left = this.right = null;
* }
* }
*/
public class Solution {
/**
* @param root: the root of the tree
* @return: the total sum of all root-to-leaf numbers
*/
public int res = 0;
public int sumNumbers(TreeNode root) {
// write your code here
return helper(root,root.val);
}
public int helper(TreeNode root,int sum){
if(root == null){
return 0;
}
if(root.left == null && root.right == null){
return sum;
}
int left = 0, right = 0;
if(root.left != null){
left = helper(root.left,sum*10+root.left.val);
}
if(root.right != null){
right = helper(root.right,sum*10+root.right.val);
}
return left+right;
}
}
