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.
/**
* 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 helper(root,0);
}
private int helper(TreeNode root,int sum){
if(root==null)
return 0;
sum=10*sum+root.val;
if(root.left==null&&root.right==null)//////////必须加上,如果不加,root 处的sum 为0!!!
return sum;
int left=helper(root.left,sum); //
int right=helper(root.right,sum);
return left+right;
}
}