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leetCode练题——12. Integer to Roman

1、题目

 

12. Integer to Roman

 

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

Symbol       Value
I             1
V             5
X             10
L             50
C             100
D             500
M             1000

For example, two is written as II in Roman numeral, just two one's added together. Twelve is written as, XII, which is simply X + II. The number twenty seven is written as XXVII, which is XX + V + II.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:

  • I can be placed before V (5) and X (10) to make 4 and 9. 
  • X can be placed before L (50) and C (100) to make 40 and 90. 
  • C can be placed before D (500) and M (1000) to make 400 and 900.

Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999.

Example 1:

Input: 3
Output: "III"

Example 2:

Input: 4
Output: "IV"

Example 3:

Input: 9
Output: "IX"

Example 4:

Input: 58
Output: "LVIII"
Explanation: L = 50, V = 5, III = 3.

Example 5:

Input: 1994
Output: "MCMXCIV"
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

2、我的解答（未简化）

 

  1 # -*- coding: utf-8 -*-
  2 # @Time    : 2020/1/30 19:14
  3 # @Author  : SmartCat0929
  4 # @Email   : 1027699719@qq.com
  5 # @Link    : https://github.com/SmartCat0929
  6 # @Site    : 
  7 # @File    : 12. Integer to Roman(自己想的复杂的算法）.py
  8 
  9 class Solution:
 10     def intToRoman(self, num: int) -> str:
 11         numStr = str(num)
 12         if num < 10:
 13             if int(numStr[-1]) > 0 and int(numStr[-1]) < 4:
 14                 units = ""
 15                 for i in range(0, int(numStr[-1])):
 16                     units = "I" + units
 17             elif int(numStr[-1]) == 4:
 18                 units = "IV"
 19             elif int(numStr[-1]) == 5:
 20                 units = "V"
 21             elif int(numStr[-1]) > 5 and int(numStr[-1]) < 9:
 22                 units = "V"
 23                 for i in range(5, int(numStr[-1])):
 24                     units = units + "I"
 25             elif int(numStr[-1]) == 9:
 26                 units = "IX"
 27             return units
 28         elif num >= 10 and num <= 99:  # 如果是两位数
 29             if int(numStr[-1]) == 0:
 30                 units = ""
 31             elif int(numStr[-1]) > 0 and int(numStr[-1]) < 4:  # 个位
 32                 units = ""
 33                 for i in range(0, int(numStr[-1])):
 34                     units = "I" + units
 35             elif int(numStr[-1]) == 4:
 36                 units = "IV"
 37             elif int(numStr[-1]) == 5:
 38                 units = "V"
 39             elif int(numStr[-1]) > 5 and int(numStr[-1]) < 9:
 40                 units = "V"
 41                 for i in range(5, int(numStr[-1])):
 42                     units = units + "I"
 43             elif int(numStr[-1]) == 9:
 44                 units = "IX"
 45             if int(numStr[-2]) == 1:  # 十位
 46                 decades = "X"
 47             elif int(numStr[-2]) > 0 and int(numStr[-2]) < 4:  # 十位
 48                 decades = ""
 49                 for j in range(0, int(numStr[-2])):
 50                     decades = "X" + decades
 51             elif int(numStr[-2]) == 4:
 52                 decades = "XL"
 53             elif int(numStr[-2]) == 5:
 54                 decades = "L"
 55             elif int(numStr[-2]) > 5 and int(numStr[-2]) < 9:
 56                 decades = "L"
 57                 for j in range(5, int(numStr[-2])):
 58                     decades = decades + "X"
 59             elif int(numStr[-2]) == 9:
 60                 decades = "XC"
 61             romans = decades + units
 62             return romans
 63 
 64         elif num >= 100 and num <= 999:  # 如果是三位数
 65             if int(numStr[-1]) == 0:  # 个位
 66                 units = ""
 67             elif int(numStr[-1]) > 0 and int(numStr[-1]) < 4:
 68                 units = ""
 69                 for i in range(0, int(numStr[-1])):
 70                     units = "I" + units
 71             elif int(numStr[-1]) == 4:
 72                 units = "IV"
 73             elif int(numStr[-1]) == 5:
 74                 units = "V"
 75             elif int(numStr[-1]) > 5 and int(numStr[-1]) < 9:
 76                 units = "V"
 77                 for i in range(5, int(numStr[-1])):
 78                     units = units + "I"
 79             elif int(numStr[-1]) == 9:
 80                 units = "IX"
 81             if int(numStr[-2]) == 0:  # 十位
 82                 decades = ""
 83             elif int(numStr[-2]) > 0 and int(numStr[-2]) < 4:
 84                 decades = ""
 85                 for j in range(0, int(numStr[-2])):
 86                     decades = "X" + decades
 87             elif int(numStr[-2]) == 4:
 88                 decades = "XL"
 89             elif int(numStr[-2]) == 5:
 90                 decades = "L"
 91             elif int(numStr[-2]) > 5 and int(numStr[-2]) < 9:
 92                 decades = "L"
 93                 for j in range(5, int(numStr[-2])):
 94                     decades = decades + "X"
 95             elif int(numStr[-2]) == 9:
 96                 decades = "XC"
 97             if int(numStr[-3]) > 0 and int(numStr[-3]) < 4:  # 百位
 98                 hundreds = ""
 99                 for j in range(0, int(numStr[-3])):
100                     hundreds = "C" + hundreds
101             elif int(numStr[-3]) == 4:
102                 hundreds = "CD"
103             elif int(numStr[-3]) == 5:
104                 hundreds = "D"
105             elif int(numStr[-3]) > 5 and int(numStr[-3]) < 9:
106                 hundreds = "D"
107                 for j in range(5, int(numStr[-3])):
108                     hundreds = hundreds + "C"
109             elif int(numStr[-3]) == 9:
110                 hundreds = "CM"
111             romans = hundreds + decades + units
112             return romans
113 
114         elif num >= 1000 and num <= 3999:  # 如果是四位数
115             if int(numStr[-1]) == 0:  # 个位
116                 units = ""
117             elif int(numStr[-1]) > 0 and int(numStr[-1]) < 4:
118                 units = ""
119                 for i in range(0, int(numStr[-1])):
120                     units = "I" + units
121             elif int(numStr[-1]) == 4:
122                 units = "IV"
123             elif int(numStr[-1]) == 5:
124                 units = "V"
125             elif int(numStr[-1]) > 5 and int(numStr[-1]) < 9:
126                 units = "V"
127                 for i in range(5, int(numStr[-1])):
128                     units = units + "I"
129             elif int(numStr[-1]) == 9:
130                 units = "IX"
131             if int(numStr[-2]) == 0:  # 十位
132                 decades = ""
133             elif int(numStr[-2]) > 0 and int(numStr[-2]) < 4:
134                 decades = ""
135                 for j in range(0, int(numStr[-2])):
136                     decades = "X" + decades
137             elif int(numStr[-2]) == 4:
138                 decades = "XL"
139             elif int(numStr[-2]) == 5:
140                 decades = "L"
141             elif int(numStr[-2]) > 5 and int(numStr[-2]) < 9:
142                 decades = "L"
143                 for j in range(5, int(numStr[-2])):
144                     decades = decades + "X"
145             elif int(numStr[-2]) == 9:
146                 decades = "XC"
147             if int(numStr[-3]) == 0:  # 百位
148                 hundreds = ""
149             elif int(numStr[-3]) > 0 and int(numStr[-3]) < 4:
150                 hundreds = ""
151                 for j in range(0, int(numStr[-3])):
152                     hundreds = "C" + hundreds
153             elif int(numStr[-3]) == 4:
154                 hundreds = "CD"
155             elif int(numStr[-3]) == 5:
156                 hundreds = "D"
157             elif int(numStr[-3]) > 5 and int(numStr[-3]) < 9:
158                 hundreds = "D"
159                 for j in range(5, int(numStr[-3])):
160                     hundreds = hundreds + "C"
161             elif int(numStr[-3]) == 9:
162                 hundreds = "CM"
163             if int(numStr[-4]) > 0 and int(numStr[-4]) < 4: #千位
164                 thousands = ""
165                 for j in range(0, int(numStr[-4])):
166                     thousands = "M" + thousands
167                 romans = thousands + hundreds + decades + units
168                 return romans
169         elif num > 3999:
170             return 0
171 
172 
173 print(Solution().intToRoman(400))
View Code

 

3、大神的解法

LeetCode上看到的大神的解法，实在是佩服！ 采用字典将特殊符号记住，随后逐一判断.......

 1 class Solution:
 2     def intToRoman(self, num: int) -> str:
 3         res = ""
 4         s = 1000
 5 
 6         d = {1: "I", 5: "V", 10: "X", 50: "L", 100: "C", 500: "D", 1000: "M"}
 7         while num != 0:
 8             r, temp = divmod(num, s)
 9 
10             if r == 9:
11                 res += d[s] + d[s * 10]
12             elif r == 4:
13                 res += d[s] + d[s * 5]
14             elif r >= 5:
15                 res += d[s * 5] + d[s] * (r - 5)
16             else:
17                 res += d[s] * r
18 
19             s = s // 10
20             num = temp
21 
22         return res
23 
24 
25 print(Solution().intToRoman(2964))

 

 

 

 

 



 







            

            
posted @ 
2020-01-30 21:23 
聪明猫 
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