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package g0101_0200.s0129_sum_root_to_leaf_numbers;

// #Medium #Depth_First_Search #Tree #Binary_Tree
// #2022_06_23_Time_0_ms_(100.00%)_Space_41.8_MB_(46.81%)

import com_github_leetcode.TreeNode;

/*
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
/**
 * 129 - Sum Root to Leaf Numbers\.
 *
 * Medium
 *
 * 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:**
 *
 * ![](https://assets.leetcode.com/uploads/2021/02/19/num1tree.jpg)
 *
 * **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:**
 *
 * ![](https://assets.leetcode.com/uploads/2021/02/19/num2tree.jpg)
 *
 * **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`.
**/
public class Solution {
    private int sum = 0;

    public int sumNumbers(TreeNode root) {
        recurseSum(root, 0);
        return sum;
    }

    private void recurseSum(TreeNode node, int curNum) {
        if (node.left == null && node.right == null) {
            sum += 10 * curNum + node.val;
        } else {
            if (node.left != null) {
                recurseSum(node.left, 10 * curNum + node.val);
            }
            if (node.right != null) {
                recurseSum(node.right, 10 * curNum + node.val);
            }
        }
    }
}




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