罗马数和整形的相互转换
1、Roman to Integer
Given a roman numeral, convert it to an integer.
Input is guaranteed to be within the range from 1 to 3999.
代码
class Solution {
public:
int romanToInt(string s) {
int res = toDecimal(s[0]);
for(int i = 1;i<s.length();i++){
if(toDecimal(s[i]) <=toDecimal(s[i-1]))
res += toDecimal(s[i]);
else
res += toDecimal(s[i]) - 2*toDecimal(s[i-1]);
}
return res;
}
int toDecimal(char c){
switch (c) {
case 'I':
return 1;
case 'V':
return 5;
case 'X':
return 10;
case 'L':
return 50;
case 'C':
return 100;
case 'D':
return 500;
case 'M':
return 1000;
default:
return 0;
}
}
};
2、 Integer to Roman
Given an integer, convert it to a roman numeral.
Input is guaranteed to be within the range from 1 to 3999.
代码
解法一
class Solution {
public:
string intToRoman(int num) {
string roman[4][10] = {
{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"},
{"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"},
{"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"},
{"", "M", "MM", "MMM"}
};
string res = "";
int index = 0;
while (num != 0) {
int digit = num % 10;
res = roman[index][digit] + res;
index++;
num /= 10;
}
return res;
}
};
解法二（打表）
class Solution {
public:
string intToRoman(int num) {
string str;
string table[13]={"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};
int value[13]= {1000,900,500,400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
for(int i=0;num!=0;i++)
{
while(num>=value[i])
{
num-=value[i];
str+=table[i];
}
}
return str;
}
};
