[LC] 129. Sum Root to Leaf Numbers
2024-09-01 18:38:28
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 path1->2represents the number12.
The root-to-leaf path1->3represents the number13.
Therefore, sum = 12 + 13 =25.
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
int res = 0;
public int sumNumbers(TreeNode root) {
helper(root, 0);
return res;
} private void helper(TreeNode root, int sum) {
if (root == null) {
return;
}
int curSum = 10 * sum + root.val;
if (root.left == null && root.right == null) {
res += curSum;
}
helper(root.left, curSum);
helper(root.right, curSum);
}
}
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