leetcode Roman Integer

最新推荐文章于 2020-06-29 15:21:54 发布

原创最新推荐文章于 2020-06-29 15:21:54 发布 · 843 阅读

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本文介绍了一种方法，用于将罗马数字转换为整数，并提供了详细的C++代码实现。同时，也展示了如何将整数转换回罗马数字，适用于1到3999范围内的数值。

Given a roman numeral, convert it to an integer.

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

class Solution {
 public:
  int romanToInt(string s) {
    if (s.length() < 1)
      return 0;
    map<char,int> m;
	m['I'] = 1;
	m['V'] = 5;
	m['X'] = 10;
	m['L'] = 50;
	m['C'] = 100;
	m['D'] = 500;
	m['M'] = 1000;    
    int i = s.length() - 1;
    int sum = m[s[i--]];
    while (i >= 0) {
      if (m[s[i + 1]] > m[s[i]])
        sum -= m[s[i]];
      else
        sum += m[s[i]];
      --i;
    }
    return sum;
  }
};

class Solution {
 public:
  string intToRoman(int num) {
    // IMPORTANT: Please reset any member data you declared, as
    // the same Solution instance will be reused for each test case.    
    string symbol[]={"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};
    int value[]={1000,900,500,400,100,90,50,40,10,9,5,4,1};  
    string res = "";
    int i = 0;
    while (num > 0) {
      if (num >= value[i]) {
        res += symbol[i];
        num -= value[i];
      }
      else
        ++i;
    }
    return res;
  }
};