func printMultiplicationTable() {
    let tableWidth = 9 * 3 + 5 + 1

    // +-------------------------------+
    var topSeparator = ""
    for index in 0..<tableWidth {
        if index == 0 || index == tableWidth - 1 {
            topSeparator += "+"
        } else {
            topSeparator += "-"
        }
    }
    print(topSeparator)

    // 九九の列の数字
    var columnNumber = "|   "
    for column in 1...9 {
        columnNumber += "  \(column)"
    }
    columnNumber += " |"
    print(columnNumber)

    // |  +----------------------------|
    var innerTopSeparator = ""
    for index in 0..<tableWidth {
        if index == 0 {
            innerTopSeparator += "|"
        } else if index > 0 && index < 3 {
            innerTopSeparator += " "
        } else if index == 3 {
            innerTopSeparator += "+"
        } else if index == tableWidth - 1 {
            innerTopSeparator += "|"
        } else {
            innerTopSeparator += "-"
        }
    }
    print(innerTopSeparator)

    // 計算結果表示
    for row in 1...9 {
        var multiplication = "| \(row)| "

        for colmun in 1...9 {
            let number = row * colmun
            var numberStr = String(number)

            if number < 10 {
                numberStr = "0" + numberStr
            }

            multiplication += numberStr + " "
        }

        multiplication += "|"
        print(multiplication)
    }

    // +-------------------------------+
    var bottomSeparator = ""
    for index in 0..<tableWidth {
        if index == 0 || index == tableWidth - 1 {
            bottomSeparator += "+"
        } else {
            bottomSeparator += "-"
        }
    }
    print(bottomSeparator)
}