129. Sum Root to Leaf Numbers

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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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 struct TreeNode {    int val;    TreeNode *left;    TreeNode *right;    TreeNode(int x) : val(x), left(NULL), right(NULL) {}};class Solution {public:int sumNumbers(TreeNode* root) {if (root == NULL) return 0;sum = 0;dfs(root, 0);return sum;}private:void dfs(TreeNode* root, int tmp){tmp = tmp * 10 + root->val;if (root->left == NULL&&root->right == NULL){sum += tmp;}if (root->left)dfs(root->left, tmp);if (root->right)dfs(root->right, tmp);}int sum;};



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