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

.

» Solve this problem

/**
* Definition for binary tree
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
int sum;
public int sumNumbers(TreeNode root) {
// Start typing your Java solution below
// DO NOT write main() function
sum = 0;
int cur = 0;
add(root,cur);
return sum;
}
public void add(TreeNode node, int cur){
if(node == null){
return;
}
cur = cur * 10 + node.val;
if(node.left == null && node.right == null){//leaves
sum += cur;
}
add(node.left,cur);
add(node.right,cur);
}
}