[LeetCode]129. Sum Root to Leaf Numbers

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.

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.

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// 递归实现/** * 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* root) {        return sumNumbers(root, 0);    }    int sumNumbers(TreeNode* root, int sum){        if(root == NULL)            return 0;        sum = sum*10 + root->val;        // 如果是叶节点，直接返回        if(root->left == NULL && root->right == NULL)            return sum;        return sumNumbers(root->left, sum) + sumNumbers(root->right, sum);    }};