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Sum Root to Leaf Numbers

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Descrpition

https://leetcode.com/problems/sum-root-to-leaf-numbers/description/

Solution

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class Solution {
public:
    int sumNumbers(TreeNode* root) {
        if (root == NULL) return 0;
        int ret = 0;
        int currentSum = 0;
        this->sumLeafNode(root, ret, currentSum);
        return ret;
    }
    
    void sumLeafNode(TreeNode* root, int& ret, int& currentSum) {
        if (root == NULL) return;
        currentSum = currentSum * 10 + root->val;
        if (root->left == NULL && root->right == NULL) ret += currentSum;
        this->sumLeafNode(root->left, ret, currentSum);
        this->sumLeafNode(root->right, ret, currentSum);
        currentSum = currentSum / 10;
    }
};