乱数作成のロジックをAWS Lambdaに移行する

1/// lib/utils/helpers/calculation_helper_mixin.dart
2
3/// ドメインに依存しない数学的計算処理
4mixin CalculationHelper {
5
6  /// nCr: n個の中からr個を選ぶ組み合わせの数
7  int getCombinationCnt(int n, int r) {
8    final permutation = _permutation(n, r);
9    final factorial = _factorial(r);
10    final result = (permutation / factorial).floor();
11    return result;
12  }
13
14  /// n!: 階乗
15  int _factorial(int n) {
16    var result = 1;
17    for (var i = 0; i < n; i++) {
18      result = result * (n - i);
19    }
20    return result;
21  }
22
23  /// nPr: n個の中からr個を選ぶ順列の数
24  int _permutation(int n, int r) {
25    var result = 1;
26    for (var i = 0; i < r; i++) {
27      result = result * (n - i);
28    }
29    return result;
30  }
31
32  /// nCr: n個の中からr個を選ぶ全ての組み合わせ
33  List<List<int>> allCombinationList(int n, int r) {
34    if (r == 0) {
35      return [[]];
36    }
37
38    if (r > n) {
39      return [];
40    }
41
42    // 1. Include the n-th element
43    final includeN = allCombinationList(n - 1, r - 1).map((comb) {
44      return [n, ...comb]
45        ..sort((a, b) => a.compareTo(b)); // sort the inner list
46    }).toList();
47
48    // 2. Exclude the n-th element
49    final excludeN = allCombinationList(n - 1, r);
50
51    // Combine the results of including and excluding the n-th element
52    // Sort the outer list based on the entire inner lists
53    final combined = [...includeN, ...excludeN]..sort((a, b) {
54        for (var i = 0; i < a.length; i++) {
55          if (a[i] != b[i]) {
56            return a[i].compareTo(b[i]);
57          }
58        }
59        return 0;
60      });
61
62    return combined;
63  }
64}
65