Leetcode048--二叉树的遍历组合相加

Posted 2022-04-16 劲火星空

一、原题

Given a binary tree containing digits from0-9only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path1->2->3which represents the number123.

Find the total sum of all root-to-leaf numbers.

For example,

    1
   / \\
  2   3

The root-to-leaf path1->2represents the number12.
The root-to-leaf path1->3represents the number13.

Return the sum = 12 + 13 =25.

一、中文

深度遍历二叉树，将每一趟深度遍历的二叉树的数字的组合进行相加，将相加的和进行返回

三、举例

比如上面就是将12和13进行相加

四、思路

其实也就是从上往下依次遍历了，一开始的时候想复杂了，进行遍历的时候进行乘十的操作

五、程序

/**
 * 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) 
        int sum = 0;
        return getSum(root, sum);
    
    
    //其实还是层序遍历
    public int getSum(TreeNode root, int sum)
        if(root == null)
            return 0;
        
        sum = sum * 10 + root.val;
        if(root.left == null && root.right == null)
            return sum;
        
        return getSum(root.left, sum) + getSum(root.right, sum);