LeetCode: Integer to Roman 解题报告

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：

http://literacy.kent.edu/Minigrants/Cinci/romanchart.htm

 package Algorithms.string;

 public class IntToRoman {
     public String intToRoman(int num) {
         int nums[] = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
         String[] romans = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};

         StringBuilder sb = new StringBuilder();

         int i = 0;
         // 使用贪心法。尽量拆分数字
         while (i < nums.length) {
             if (num >= nums[i]) {
                 sb.append(romans[i]);
                 num -= nums[i];
             } else {
                 i++;
             }
         }

         return sb.toString();
     }
 }

2015.1.12 redo:

 public String intToRoman(int num) {
         int[] nums = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};

         /*
             1000, 900, 500, 400, 100,  90,   50,   40,  10, 9, 5, 4, 1
             "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X" IX V, IV, I
         */
         String[] strs = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};

         int i = 0;
         StringBuilder sb = new StringBuilder();
         // greedy.
         while (i < nums.length) {
             // bug 1: should use ">="
             if (num >= nums[i]) {
                 sb.append(strs[i]);
                 // bug 2: should remember to reduce the nums[i].
                 num -= nums[i];
             } else {
                 i++;
             }
         }

         return sb.toString();
     }

请至主页君GITHUB:

https://github.com/yuzhangcmu/LeetCode_algorithm/blob/master/string/IntToRoman.java