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.
睡前刷一题。把每一条从根到叶子的路径经过的数字拼起来组成一个数，求这些数的和。 简单的DFS题，不解释。完整代码如下：
class Solution {
public:
void dfs(int& sum, int sub_sum, TreeNode* root)
{
if (root->left == NULL && root->right == NULL) {
sum += (sub_sum * 10 + root->val);
return;
}
if (root->left != NULL)
dfs(sum, sub_sum * 10 + root->val, root->left);
if (root->right != NULL)
dfs(sum, sub_sum * 10 + root->val, root->right);
}
int sumNumbers(TreeNode* root)
{
if (root == NULL)
return 0;
int sum = 0;
dfs(sum, 0, root);
return sum;
}
};本代码提交AC，用时3MS。