129 Sum Root to Leaf Numbers – Medium
Problem:
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.
Thoughts:
This is a very basic recursion problem. Binary Tree iteration.
Solutions:
/**
* Definition for a binary tree node.
* 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 sum(root, "");
}
private int sum(TreeNode root, String curr){
if (root.left == null && root.right == null) {
return Integer.parseInt(curr + root.val);
}
int sums = 0;
if (root.left != null) {
sums += sum(root.left, curr + root.val);
}
if (root.right != null) {
sums += sum(root.right, curr + root.val);
}
return sums;
}
}