Integer to Roman

Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.

SOLUTION 1:

从大到小的贪心写法。从大到小匹配，尽量多地匹配当前的字符。

罗马数字对照表：

1 package Algorithms.string; 2  3 public class IntToRoman { 4     public String intToRoman(int num) { 5         int nums[] = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1}; 6         String[] romans = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"}; 7      8         StringBuilder sb = new StringBuilder(); 9         10         int i = 0;11         // 使用贪心法。尽量拆分数字12         while (i < nums.length) {13             if (num >= nums[i]) {14                 sb.append(romans[i]);15                 num -= nums[i];16             } else {17                 i++;18             }19         }20         21         return sb.toString();22     }23 }

 2015.1.12 redo:

1 public String intToRoman(int num) { 2         int[] nums = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1}; 3          4         /* 5             1000, 900, 500, 400, 100,  90,   50,   40,  10, 9, 5, 4, 1 6             "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X" IX V, IV, I 7         */ 8         String[] strs = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"}; 9         10         int i = 0;11         StringBuilder sb = new StringBuilder();12         // greedy.13         while (i < nums.length) {14             // bug 1: should use ">="15             if (num >= nums[i]) {16                 sb.append(strs[i]);17                 // bug 2: should remember to reduce the nums[i].18                 num -= nums[i];19             } else {20                 i++;21             }22         }23         24         return sb.toString();25     }

 

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