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[leetcode]Sum Root to Leaf Numbers

2024-07-17 20:58:14   223人阅读

Sum Root to Leaf Numbers

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.

算法思路：

DFS。

代码如下：

 1 /** 2  * Definition for binary tree 3  * public class TreeNode { 4  *     int val; 5  *     TreeNode left; 6  *     TreeNode right; 7  *     TreeNode(int x) { val = x; } 8  * } 9  */10 public class Solution {11     int res = 0;12     public int sumNumbers(TreeNode root){13         if(root == null) return res;14         dfs(root,0);15         return res;16     }17     private void dfs(TreeNode root,int num){18         if(root == null) return;19         if(root.left == null && root.right == null){20             res += 10 * num + root.val;21             return;22         }23         num = num * 10 + root.val;24         if(root.left != null){25             dfs(root.left,num);26         }27         if(root.right != null){28             dfs(root.right,num);29         }30     }31     32 }

 


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