LeetCode 0129 - Sum Root to Leaf Numbers

Reck Zhang

发布于 2021-08-11 14:36:49

1980

发布于 2021-08-11 14:36:49

文章被收录于专栏：Reck Zhang

Sum Root to Leaf Numbers

Desicription

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.

Example 2:

Input: [4,9,0,5,1]
    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.

Solution

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int sumNumbers(TreeNode* currentRoot, int currentSum = 0) {
        if(currentRoot == NULL)
            return 0;
        if(currentRoot->left == NULL && currentRoot->right == NULL)
            return currentSum * 10 + currentRoot->val;
        return sumNumbers(currentRoot->left, currentSum * 10 + currentRoot->val) + 
               sumNumbers(currentRoot->right, currentSum * 10 + currentRoot->val);
    }
};

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原始发表：2018-05-24，如有侵权请联系 cloudcommunity@tencent.com 删除

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