129. Sum Root to Leaf Numbers
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); } }