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:
    js与设计模式访问者模式
    js与设计模式外观模式
    由一个小Bug推及ie及ff的dom元素差异
    构建一个前端库做一个富客户端的基类
    [原创]LINQ 学习系列教程文章索引
    Sublime Text 2 性感无比的代码编辑器!程序员必备神器!跨平台支持Win/Mac/Linux
    Ubuntu分区
    非常不错的WCF入门文章,来自Artech
    助记:MIME类型
    F#学习存疑求解答:关于使用Cotinuation仍然堆栈溢出的问题
  • 原文地址:https://www.cnblogs.com/xuanlu/p/12131138.html
Copyright © 2011-2022 走看看