leetcode记录12.Integer to Roman

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本文介绍了一种将整数转换为罗马数字的算法实现，详细解析了罗马数字的书写规则，包括特殊情况的处理，如四和九的表示。通过Python代码展示了如何逐位处理整数，使用循环和条件判断生成对应的罗马数字。

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leetcode记录12.Integer to Roman

#
# @lc app=leetcode id=12 lang=python3
#
# [12] Integer to Roman
#
# https:leetcode.com//problems//integer-to-roman//description//
#
# algorithms
# Medium (49.89%)
# Total Accepted:    207.1K
# Total Submissions: 415.2K
# Testcase Example:  '3'
#
# 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.
# 
#
class Solution:
    def intToRoman(self, num: int) -> str:
        result = ''
        if num // 1000 != 0:
            for i in range(num // 1000):
                result += 'M'
            num = num % 1000
        if num // 900 != 0:
            for i in range(num // 900):
                result += 'CM'
            num = num % 900
        if num // 500 != 0:
            for i in range(num // 500):
                result += 'D'
            num = num % 500
        if num // 400 != 0:
            for i in range(num // 400):
                result += 'CD'
            num = num % 400
        if num // 100 != 0:
            for i in range(num // 100):
                result += 'C'
            num = num % 100
        if num // 90 != 0:
            for i in range(num // 90):
                result += 'XC'
            num = num % 90
        if num // 50 != 0:
            for i in range(num // 50):
                result += 'L'
            num = num % 50
        if num // 40 != 0:
            for i in range(num // 40):
                result += 'XL'
            num = num % 40
        if num // 10 != 0:
            for i in range(num // 10):
                result += 'X'
            num = num % 10
        if num // 9 != 0:
            for i in range(num // 9):
                result += 'IX'
            num = num % 9
        if num // 5 != 0:
            for i in range(num // 5):
                result += 'V'
            num = num % 5
        if num // 4 != 0:
            for i in range(num // 4):
                result += 'IV'
            num = num % 4
        if num // 1 != 0:
            for i in range(num // 1):
                result += 'I'
            num = num % 1
        return result