LeetCode 129: Sum Root to Leaf Numbers

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.

解题思路

/** * 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 {private:    void dfs(TreeNode *root, int num, int &sum) {        if (root == NULL) return;        num = num * 10 + root->val;        if (root->left == NULL && root->right == NULL) {            sum += num;        }        else {            dfs(root->left, num, sum);            dfs(root->right, num, sum);        }    }public:    int sumNumbers(TreeNode* root) {        int sum = 0;        dfs(root, 0, sum);        return sum;    }};