Question Definition
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.
Java Solution
public int sumNumbers(TreeNode root) {
return helper(root, 0);
}
private int helper(TreeNode root, int parent) {
if(root == null) return parent;
parent = parent * 10 + root.val;
int result = 0;
if(root.left != null)
result += helper(root.left, parent);
if(root.right != null)
result += helper(root.right, parent);
if(root.left == null && root.right == null)
result = parent;
return result;
}
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