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class Solution {
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  public int sumOfLeftLeaves(TreeNode root) {
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    if (root == null) return 0;
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    if (root.left != null && root.left.left == null && root.left.right == null) {
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      return root.left.val + sumOfLeftLeaves(root.left) + sumOfLeftLeaves(root.right);
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    } else {
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      return sumOfLeftLeaves(root.left) + sumOfLeftLeaves(root.right);
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    }
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  }
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}