# DAY 27
0
AI & Data

## 找LeetCode上簡單的題目來撐過30天啦(DAY27)

You are given the root of a binary tree containing digits from 0 to 9 only.
Each root-to-leaf path in the tree represents a number.
• For example, the root-to-leaf path 1 -> 2 -> 3 represents the number 123.
Return the total sum of all root-to-leaf numbers. Test cases are generated so that the answer will fit in a 32-bit integer.
A leaf node is a node with no children.

Example 1: Input: root = [1,2,3]
Output: 25
Explanation:
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.
Therefore, sum = 12 + 13 = 25.
Example 2: Input: root = [4,9,0,5,1]
Output: 1026
Explanation:
The root-to-leaf path 4->9->5 represents the number 495.
The root-to-leaf path 4->9->1 represents the number 491.
The root-to-leaf path 4->0 represents the number 40.
Therefore, sum = 495 + 491 + 40 = 1026.

Constraints:
• The number of nodes in the tree is in the range [1, 1000].
• 0 <= Node.val <= 9
• The depth of the tree will not exceed 10.

``````class Solution {
public int sumNumbers(TreeNode root) {
if(root == null){
return 0;
}else if(root.left==null && root.right==null){
return root.val;
}
TreeNode current = root;
int resultf = 0;
return chk(root,resultf);
}

public int chk(TreeNode now,int result) {
result = result*10 +now.val;
if(now.left==null && now.right == null){
return result;
}
if(now.left==null){
return chk(now.right,result);
}else if(now.right==null){
return chk(now.left,result);
}
return chk(now.left,result) + chk(now.right,result);
}

}
``````

DAY27心得