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class Solution {
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  int res;
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  public int sumNumbers(TreeNode root) {
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    res = 0;
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    getSum(root, 0);
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    return res;
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  }
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  public void getSum(TreeNode root, int sum) {
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    if (root.left == null && root.right == null) {
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      res += (sum * 10 + root.val);
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    }
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    if (root.left != null) getSum(root.left, sum * 10 + root.val);
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    if (root.right != null) getSum(root.right, sum * 10 + root.val);
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  }
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}