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

 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 }
View Code

 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     }
View Code

 

请至主页君GITHUB:

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

 

posted on 2014-11-23 17:06  Yu's Garden  阅读(545)  评论(0)  编辑  收藏  举报

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