【LeetCode】Sum Root to Leaf Numbers

제목
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.
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 .
해답
나무의 귀속으로 해결하다
/**
 * 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);
    }
    
    public int sum(TreeNode node,int parentVal){
        int sum=0;
        int temp=parentVal*10+node.val;
        if(node.left==null&&node.right==null){
            sum=temp;
        }
        if(node.left!=null){
            sum+=sum(node.left,temp);
        }
        if(node.right!=null){
            sum+=sum(node.right,temp);
        }
        return sum;
    }
} 

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