【Swift】2次元配列 で 転置行列 ( transpose matrix ) 👉 https://android.benigumo.com/20240201/transpose-matrix/

transpose-matrix.swift

extension Collection where Element: Collection,
                           Self.Index == Int, Element.Index == Int {

  func transposed1() -> [[Element.Element]] {
    let cols = 0 ..< (self.first?.count ?? 0)
    let rows = 0 ..< self.count
    var result: [[Element.Element]] = []
    for col in cols {
      var newRow: [Element.Element] = []
      for row in rows {
        newRow.append(self[row][col])
      }
      result.append(newRow)
    }
    return result
  }

  func transposed2() -> [[Element.Element]] {
    let cols = 0 ..< (self.first?.count ?? 0)
    let rows = 0 ..< self.count
    return cols.map { col in
      rows.map { row in
        self[row][col]
      }
    }
  }

  func transposed3() -> [[Element.Element]] {
    return (0 ..< (first?.count ?? 0)).map { col in
      (0 ..< count).map { row in
        self[row][col]
      }
    }
  }
}

let d = [
  [  1,   2,   3,   4,   5],
  ["A", "B", "C", "D", "E"],
  ["あ", "い", "う", "え", "お"],
  ["か", "き", "く", "け", "こ"]
]

print(d)
print(d.transposed1())
print(d.transposed2())
print(d.transposed3())

// [[1, 2, 3, 4, 5], ["A", "B", "C", "D", "E"], ["あ", "い", "う", "え", "お"], ["か", "き", "く", "け", "こ"]]
// [[1, "A", "あ", "か"], [2, "B", "い", "き"], [3, "C", "う", "く"], [4, "D", "え", "け"], [5, "E", "お", "こ"]]
// [[1, "A", "あ", "か"], [2, "B", "い", "き"], [3, "C", "う", "く"], [4, "D", "え", "け"], [5, "E", "お", "こ"]]
// [[1, "A", "あ", "か"], [2, "B", "い", "き"], [3, "C", "う", "く"], [4, "D", "え", "け"], [5, "E", "お", "こ"]]