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