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.
计算所有路径的和,从根节点到叶子节点每条路径都代表一个十进制的数字。用递归从根节点开始,依次记录所有路径上组成数字的和。代码如下:
/** * 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) { if(root == null) return 0; return sum(root, root.val); } public int sum(TreeNode root, int value) { if(root == null) return value; if(root.left != null && root.right != null) return sum(root.left, value * 10 +root.left.val) + sum(root.right, value * 10 + root.right.val); if(root.left != null) return sum(root.left, value * 10 +root.left.val); if(root.right != null) return sum(root.right, value * 10 + root.right.val); return value; } }