[leetcode]12. Integer to Roman

做好分类，注意边界。

Success

Details 

Runtime: 52 ms, faster than 98.97% of Python3 online submissions forInteger to Roman.

Memory Usage: 13.3 MB, less than 60.15% of Python3 online submissions for Integer to Roman.

 

Submission Detail

3999 / 3999 test cases passed.	Status:  Accepted
Runtime: 52 ms Memory Usage: 13.3 MB	Submitted: 0 minutes ago

class Solution:
    def intToRoman(self, num: int) -> str:
        if 1000 <= num <= 3999:
            units_digit = num % 10
            tens_digit = num % 100 - units_digit
            hundreds_digit = num%1000 - tens_digit - units_digit
            thousands_digit = num //1000
            units_ret = Solution().dealunitsdigit(units_digit)
            tens_ret = Solution().dealtensdigit(tens_digit)
            hundreds_ret = Solution().dealhundredsdigit(hundreds_digit)
            thousands_ret = ""
            for index in range(thousands_digit):
                thousands_ret = thousands_ret + "M"
            return thousands_ret + hundreds_ret + tens_ret + units_ret
        elif 100 <= num < 1000:
            units_digit = num %10
            tens_digit = num%100 - units_digit
            hundreds_digit = num - tens_digit - units_digit
            units_ret = Solution().dealunitsdigit(units_digit)
            tens_ret = Solution().dealtensdigit(tens_digit)
            hundreds_ret = Solution().dealhundredsdigit(hundreds_digit)
            return hundreds_ret + tens_ret + units_ret
        elif 10 <= num < 100:
            units_digit = num %10
            tens_digit = num - units_digit
            units_ret = Solution().dealunitsdigit(units_digit)
            tens_ret = Solution().dealtensdigit(tens_digit)
            return tens_ret + units_ret
        elif 1 <= num < 10:
            ret = Solution().dealunitsdigit(num)
            return ret
    #1-9
    def dealunitsdigit(self,num:int) -> str:
        if num == 0:
            return ""
        if num == 4:
            return "IV"
        if num == 9:
            return "IX"
        if num <5:
            ret =""
            for index in range(num):
                ret = ret + "I"
            return ret
        else:
            ret ="V"
            for index in range(num -5): #min V
                ret = ret + "I"
            return ret
    #10,20,30,40...90
    def dealtensdigit(self,num:int) -> str:
        if num == 40:
            return "XL"
        if num == 90:
            return "XC"
        if num <50:
            ret =""
            for index in range(num//10):
                ret = ret + "X"
            return ret
        else:
            ret ="L"
            for index in range((num -50)//10): #min L
                ret = ret + "X"
            return ret
    #100,200,300...900
    def dealhundredsdigit(self,num:int) -> str:
        if num == 400:
            return "CD"
        if num == 900:
            return "CM"
        if num <500:
            ret =""
            for index in range(num//100):
                ret = ret + "C"
            return ret
        else:
            ret ="D"
            for index in range((num -500)//100): #min L
                ret = ret + "C"
            return ret