leetcode 129

class Solution {
public:
	int ans;
public:
	void dfs(TreeNode* root, int curNum) {
		if (!root) return ;
		curNum = curNum*10 + root->val;
		auto left = root->left;
		auto right = root->right;
		if (!left && !right) ans += curNum;
		dfs(left, curNum);
		dfs(right, curNum);
		curNum /= 10;
	}
	int sumNumbers(TreeNode* root){
		dfs(root, 0);
		return ans;
	}

};
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