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  • [LC] 129. 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.

    Note: A leaf is a node with no children.

    Example:

    Input: [1,2,3]
        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.

    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     *     int val;
     *     TreeNode left;
     *     TreeNode right;
     *     TreeNode(int x) { val = x; }
     * }
     */
    class Solution {
        int res = 0;
        public int sumNumbers(TreeNode root) {
            helper(root, 0);
            return res;
        }
        
        private void helper(TreeNode root, int sum) {
            if (root == null) {
                return;
            }
            int curSum = 10 * sum + root.val;
            if (root.left == null && root.right == null) {
                res += curSum;
            }
            helper(root.left, curSum);
            helper(root.right, curSum);
        }
    }
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  • 原文地址:https://www.cnblogs.com/xuanlu/p/12028384.html
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