Sum Root to Leaf Numbers

Finally completed the Leetcode on the AC rate of more than 30% of the topic, the problem is the last, to commemorate a bit.

The original question is like this:

Given a binary tree containing digits from only 0-9 , 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.

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 = + = 25 .

Thinking of solving problems: recursion

The code is as follows:

public class Sumroottoleafnumbers {public int sumnumbers (TreeNode root) {if (root = null) {return 0;} else {return sum (RO OT, 0);}} public int sum (TreeNode root, int prev) {if (Root.left = = NULL && Root.right = = null) {return * prev + root.val ;} else if (Root.left = null && root.right! = null) {return sum (root.left, prev * + root.val) + sum (root.right, PR EV * + root.val);} else if (root.left! = null) {return sum (root.left, prev * + root.val);} else {return sum (root.right, prev * + ROOT.V AL);}}}

Sum Root to Leaf Numbers