129. Sum Root to Leaf Numbers
摘要：
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-&g...
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 / \ 23 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 / \ 90 / \ 51 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.
難度：medium
題目：給定結點值只包含0-9的二叉樹，每條從根到葉子的路徑表示一個整數。找出所有這樣的數並返回其和。
注意：葉結點即沒有左右子結點
/**
* Definition for a binary tree node.
* public class TreeNode {
*int val;
*TreeNode left;
*TreeNode right;
*TreeNode(int x) { val = x; }
* }
*/
class Solution {
public int sumNumbers(TreeNode root) {
return sumNumbers(root, "");
}
private int sumNumbers(TreeNode root, String s) {
if (null == root) {
return 0;
}
s += root.val;
if (null == root.left && null == root.right) {
return Integer.parseInt(s);
}
return sumNumbers(root.left, s) + sumNumbers(root.right, s);
}
}