class Solution {public:    int sumNumbers(TreeNode* root) {        return sumNumbersDFS(root, 0);    }    int sumNumbersDFS(TreeNode* root, int sum) {        if (!root) return 0;        sum = sum * 10 + root->val;        if (!root->left && !root->right) return sum;        return sumNumbersDFS(root->left, sum) + sumNumbersDFS(root->right, sum);    }};

class Solution {public:    int sumNumbers(TreeNode* root) {        if (!root) return 0;        int res = 0;        stack
    
      st{
   {root}};        while (!st.empty()) {            TreeNode *t = st.top(); st.pop();            if (!t->left && !t->right) {                res += t->val;            }            if (t->right) {                t->right->val += t->val * 10;                st.push(t->right);            }            if (t->left) {                t->left->val += t->val * 10;                st.push(t->left);            }        }        return res;    }};