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

    Roman numerals are represented by seven different symbols: IVXLCD 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.
    //Time: O(n), Space: O(1)
    //注意:由于i停止是在倒数第二位,所以跳出循环再把最后一个一位加上
    public int romanToInt(String s) { if (s == null || s.length() == 0) { return 0; } int result = 0; for (int i = 0; i < s.length() - 1; i++) { int cur = map(s.charAt(i)); int next = map(s.charAt(i + 1)); if (cur >= next) { result += cur; } else { result -= cur; } } return result + map(s.charAt(s.length() - 1)); } private int map(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; } }
  • 相关阅读:
    JavaScript语法
    javascript的用法
    格式和布局
    Css样式表
    HTML基本语言(表单的基本元素)
    HTML超文本语言(一般标签)
    C#项目打开/保存文件夹/指定类型文件,获取路径
    在DataGridView控件中加入ComboBox下拉列表框的实现
    DataGridView 中添加CheckBox和常用处理方式 .
    数据库建模模板、菜单显示出问题解决方案
  • 原文地址:https://www.cnblogs.com/jessie2009/p/9772340.html
Copyright © 2011-2022 走看看