问题描述
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 a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.
Example 1:
Input: "III" Output: 3 Example 2:
Input: "IV" Output: 4 Example 3:
Input: "IX" Output: 9 Example 4:
Input: "LVIII" Output: 58 Explanation: L = 50, V= 5, III = 3. Example 5:
Input: "MCMXCIV" Output: 1994 Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
把罗马数字转换成数字。
解题思路
- 读取罗马数字，每次读两位
- 如果下一位比当前位代表的数字大，则表示要用下一位的数字减去当前位数字。
- 否则就加上当前位代表的数字。
代码实现
代码语言：javascript复制class Solution {
public int romanToInt(String s) {
int result = 0;
for(int i = 0; i < s.length(); i ) {
int currentNum = getIntFromChar(s.charAt(i));
if (i 1 < s.length()) {
int nextNum = getIntFromChar(s.charAt(i 1));
if (currentNum < nextNum) {
result = result (nextNum - currentNum);
i = i 1;
} else {
result = currentNum;
}
} else {
result = currentNum;
}
}
return result;
}
private int getIntFromChar(char input){
switch(input){
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;
}
}
}
