Binary Tree Paths LeetCode solution in Java

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class Solution {
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  public List<String> binaryTreePaths(TreeNode root) {
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    List<String> result = new ArrayList<>();
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    dfs(root, new StringBuilder(), result);
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    return result;
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  }
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  private void dfs(TreeNode node, StringBuilder path, List<String> result) {
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    if (node == null) return;
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    int len = path.length();
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    if (len > 0) {
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      path.append("->");
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    }
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    path.append(node.val);
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    if (node.left == null && node.right == null) {
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      result.add(path.toString());
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    } else {
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      dfs(node.left, path, result);
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      dfs(node.right, path, result);
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    }
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    path.setLength(len); // Backtrack by resetting the StringBuilder
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  }
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}