zoukankan      html  css  js  c++  java
  • [LC] 13. Roman to Integer

    Roman numerals are represented by seven different symbols: IVXLCDand 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.

    class Solution {
        public int romanToInt(String s) {
            if (s == null || s.length() == 0) {
                return 0;
            } 
            Map<Character, Integer> myMap = getMap();
            int res = myMap.get(s.charAt(0));
            for(int i = 1; i < s.length(); i++) {
                // for case of IV =  1 + 5 - 2 * 1
                if (myMap.get(s.charAt(i)) > myMap.get(s.charAt(i - 1))) {
                    res += myMap.get(s.charAt(i)) - 2 * myMap.get(s.charAt(i - 1));
                } else {
                    res += myMap.get(s.charAt(i));
                }
            }
            return res;        
        }
        
        private Map<Character, Integer> getMap() {
            Map<Character, Integer> myMap = new HashMap<>();
            myMap.put('I', 1);
            myMap.put('V', 5);
            myMap.put('X', 10);
            myMap.put('L', 50);
            myMap.put('C', 100);
            myMap.put('D', 500);
            myMap.put('M', 1000);
            return myMap;
        }
    }
  • 相关阅读:
    phpcms URL
    域名加前后缀
    8、对象Object
    7、数组Array
    6、函数返回值、this、递归及回调函数
    5、函数、声明提前、作用域及函数参数
    4、while、dowhile、for、嵌套循环及关键字
    3、分支、if及switch语句
    2、js运算及进制
    1、JavaScript数据类型及输出
  • 原文地址:https://www.cnblogs.com/xuanlu/p/12131138.html
Copyright © 2011-2022 走看看