这题thumps down怎么这么多，反正叫我徒手写是不可能写得出来的，记下来吧
首先要直到罗马数字和阿拉伯数字的转换规则：
image.png
- Integer to Roman
class Solution {
// I 1
// V 5
// X 10
// L 50
// C 100
// D 500
// M 1000
public String intToRoman(int num) {
String M[] = {"", "M","MM","MMM"};
String C[] = {"", "C","CC","CCC","CD","D","DC","DCC","DCCC","CM"};
String X[] = {"","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"};
String I[] = {"", "I","II","III","IV","V","VI","VII","VIII","IX"};
return M[num/1000] + C[num%1000/100] + X[num%100/10] + I[num%10];
}
}
- Roman to Integer
很少写switch case, 注意一下syntax:
switch (variable){
case 'v1':
do sth;
break;
case 'v1':
do sth;
break;
}
class Solution {
public int romanToInt(String s) {
int res = 0;
// I 1
// V 5
// X 10
// L 50
// C 100
// D 500
// M 1000
//"XXIV"
//"XXII"
for (int i = s.length() - 1; i >= 0; i--){
char c = s.charAt(i);
switch (c) {
case 'I':
res += (res >= 5 ? -1 : 1);
break;
case 'V':
res += 5;
break;
case 'X':
res += (res >= 50 ? -10 : 10);
break;
case 'L':
res += 50;
break;
case 'C':
res += (res >= 500 ? -100 : 100);
break;
case 'D':
res += 500;
break;
case 'M':
res += 1000;
break;
}
}
return res;
}
}
