1. import java.util.ArrayList;
  2. import java.util.List;
  4. class DataAggregator {
  6. /**
  7. * Aggregates values from a list of datasets.
  8. *
  9. * @param datasets A list of datasets, where each dataset is a list of numbers.
  10. * @return A list containing the aggregated values (sum of each corresponding element).
  11. * Returns an empty list if the input is null or empty.
  12. * Returns null if datasets have different lengths.
  13. */
  14. public static List<Double> aggregateDatasets(List<List<Double>> datasets) {
  15. if (datasets == null || datasets.isEmpty()) {
  16. return new ArrayList<>(); // Return empty list for null or empty input
  17. }
  19. int numDatasets = datasets.size();
  20. int datasetLength = datasets.get(0).size();
  22. // Check if all datasets have the same length
  23. for (List<Double> dataset : datasets) {
  24. if (dataset.size() != datasetLength) {
  25. return null; // Return null if datasets have different lengths
  26. }
  27. }
  29. List<Double> aggregatedValues = new ArrayList<>(datasetLength); // Initialize with correct size
  30. for (int i = 0; i < datasetLength; i++) {
  31. double sum = 0.0;
  32. for (List<Double> dataset : datasets) {
  33. sum += dataset.get(i); // Sum the values at the same index
  34. }
  35. aggregatedValues.add(sum); // Add the sum to the aggregated list
  36. }
  38. return aggregatedValues;
  39. }
  41. public static void main(String[] args) {
  42. //Example Usage
  43. List<List<Double>> datasets = new ArrayList<>();
  44. datasets.add(List.of(1.0, 2.0, 3.0));
  45. datasets.add(List.of(4.0, 5.0, 6.0));
  46. datasets.add(List.of(7.0, 8.0, 9.0));
  48. List<Double> aggregated = aggregateDatasets(datasets);
  50. if (aggregated != null) {
  51. System.out.println("Aggregated values: " + aggregated); // Output: [12.0, 15.0, 18.0]
  52. } else {
  53. System.out.println("Datasets have different lengths.");
  54. }
  56. // Test case with different lengths
  57. List<List<Double>> datasets2 = new ArrayList<>();
  58. datasets2.add(List.of(1.0, 2.0));
  59. datasets2.add(List.of(3.0, 4.0, 5.0));
  61. List<Double> aggregated2 = aggregateDatasets(datasets2);
  63. if (aggregated2 == null) {
  64. System.out.println("Datasets have different lengths.");
  65. }
  67. //Test with empty list
  68. List<List<Double>> datasets3 = new ArrayList<>();
  69. List<Double> aggregated3 = aggregateDatasets(datasets3);
  70. System.out.println("Aggregated values (empty list): " + aggregated3); //Output: []
  71. }
  72. }

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