Leetcode 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.

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 0;
    sum = root->val+sum*10;
    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 0;
    int sum = root->val;
    if(root-> left == NULL && root->right ==NULL) return sum;
    
    return dfs(root->left,sum) + dfs(root->right, sum);
}