"Leetcode" Sum Root to Leaf Numbers

Topic

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 .

Answer

The topic asks for the number of all roots to the composition of the path of the leaves. After each layer is traversed, the values are *10, so a recursive approach can be considered. Refer to others, the code is as follows:

/** * Definition for Binary tree * 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,0);    }        private int sum (TreeNode root,int parentval) {        if (root==null) {            return 0;        }        int sum=0;        int temp=10*parentval+root.val;        if (root.left==null&&root.right==null) {  //Note the value is assigned to sum sum=temp only if the node is a leaf node            ;        }        if (root.left!=null) {            sum+=sum (root.left,temp);        }        if (root.right!=null) {            sum+=sum (root.right,temp);        }        return sum;    }}
   

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"Leetcode" Sum Root to Leaf Numbers