Leetcode | Roman to Integer & Integer to Roman

最新推荐文章于 2019-06-11 20:25:26 发布

转载最新推荐文章于 2019-06-11 20:25:26 发布 · 54 阅读

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原文链接：http://www.cnblogs.com/linyx/p/3986686.html

本文提供了一种简洁的方法来实现罗马数字到整数的转换，同时也介绍了整数到罗马数字的转换算法。通过简单的代码示例，展示了如何在C++中实现这两种转换。

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Roman to Integer

Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.

搜了一下，才知道这道题可以写这么简洁。

 1 class Solution {
 2 public:
 3     int romanToInt(string s) {
 4         if (s.empty()) return 0;
 5         int dict[100];
 6         dict['I'] = 1; dict['V'] = 5; dict['X'] = 10; dict['L'] = 50;
 7         dict['C'] = 100; dict['D'] = 500; dict['M'] = 1000;
 8     
 9         int ans = dict[s[0]];
10         for (int i = 1; i < s.length(); ++i) {
11             if (dict[s[i]] <= dict[s[i - 1]]) {
12                 ans += dict[s[i]];
13             } else {
14                 ans = ans - 2 * dict[s[i - 1]] + dict[s[i]];
15             }
16         }
17         return ans;
18     }
19 };

Integer to Roman

Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.

 1 class Solution {
 2 public:
 3     string intToRoman(int num) {
 4         string str[] = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
 5         int value[] = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
 6         
 7         string ret = "";
 8         for (int i = 0; i < 13; ++i) {
 9             while (num >= value[i]) {
10                 ret += str[i];
11                 num -= value[i];
12             }
13         }
14         return ret;
15     }
16 };