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.
本题利用利用深搜到叶子节点，同时记录下sum即可
int dfs(TreeNode *root, int sum){
if(root == NULL) return ;
sum = root->val+sum*;
if(root->left == NULL && root->right == NULL) return sum;
return dfs(root->left,sum)+dfs(root->right,sum);
}
int sumNumbers(TreeNode *root){
if(root == NULL ) return ;
int sum = root->val;
if(root-> left == NULL && root->right ==NULL) return sum;
return dfs(root->left,sum) + dfs(root->right, sum);
}