129. Sum Root to Leaf Numbers

解題心得

把 tree 給走訪一遍。若走到 left node 就把累計的加起來。

程式碼

class Solution {
public:
    void helper(TreeNode* root, int& sum, int current)
    {
        current = current * 10 + root->val;
        if(root->left == nullptr && root->right == nullptr)
        {
            sum += current;
            cout << current << endl;
            return;
        }
        else
        {
            if(root->left) helper(root->left, sum, current);
            if(root->right) helper(root->right, sum, current);
        }
    }
    int sumNumbers(TreeNode* root) {
        int sum = 0;
        helper(root, sum, 0);
        return sum;
    }
};